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The Affective Reactivity Index: a concise irritability scale for clinical and research settings

The Affective Reactivity Index: a concise irritability scale for clinical and research settings Journal of Child Psychology and Psychiatry 53:11 (2012), pp 1109–1117 doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index: a concise irritability scale for clinical and research settings 1 1 1 2 Argyris Stringaris , Robert Goodman , Sumudu Ferdinando , Varun Razdan , 2 2 2 Eli Muhrer , Ellen Leibenluft and Melissa A. Brotman King’s College London, Institute of Psychiatry, Denmark Hill, London, UK Section on Bipolar Spectrum Disorders, Emotion and Development Branch, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD USA Background: Irritable mood has recently become a matter of intense scientific interest. Here, we present data from two samples, one from the United States and the other from the United Kingdom, demon- strating the clinical and research utility of the parent- and self-report forms of the Affective Reactivity Index (ARI), a concise dimensional measure of irritability. Methods: The US sample (n = 218) consisted of children and adolescents recruited at the National Institute of Mental Health meeting criteria for bipolar disorder (BD, n = 39), severe mood dysregulation (SMD, n = 67), children at family risk for BD (n = 35), or were healthy volunteers (n = 77). The UK sample (n = 88) was comprised of children from a generic mental health setting and healthy volunteers from primary and secondary schools. Results: Parent- and self- report scales of the ARI showed excellent internal consistencies and formed a single factor in the two samples. In the US sample, the ARI showed a gradation with irritability significantly increasing from healthy volunteers through to SMD. Irritability was significantly higher in SMD than in BD by parent- report, but this did not reach significance by self-report. In the UK sample, parent-rated irritability was differentially related to emotional problems. Conclusions: Irritability can be measured using a concise instrument both in a highly specialized US, as well as a general UK child mental health setting. Keywords: Mood dysregulation, Affective Reactivity Index, irritability, depression, bipolar and temper outbursts (Stringaris, 2011). Respon- Introduction dents rate irritability over the last 6 months. The scale Recently, irritable mood has become a focus of in- focuses on chronic irritability (Leibenluft, Cohen, tense scientific interest (Leibenluft, 2011; Stringaris, Gorrindo, Brook, & Pine, 2006). This presents com- 2011). However, research on the measurement of monly as a child who is described by his/her parents irritability has been limited. This study reports the as ‘always angry’ and as reacting with intense anger to psychometric properties of a concise irritability situations that other children would take in their measure for use in clinical practice and research. stride. This differs from the less usual presentation of While irritability is listed as a symptom for multi- irritability occurring as part of a circumscribed epi- ple diagnoses, the term is not defined in the DSM-IV sode (APA, 2000; Leibenluft et al., 2006). (APA, 2000), and there is no consensus definition in Specifically, the ARI scale was designed to exam- the literature. Moreover, despite the intense interest ine, in a way accessible to most children and par- of the DSM-5 taskforce in irritability, defined both ents, three aspects of irritability: (a) threshold for an dimensionally and categorically (APA, 2011a,b), angry reaction; (b) frequency of angry feelings/ research on the measurement of irritability has been behaviors; (c) duration of such feelings/behaviors. limited. This is unfortunate, given the importance The scale was designed to ascertain irritable mood ascribed to studying the dimensional structure of rather than its possible consequences such as hos- psychopathology and its neurobiological underpin- tility [i.e., dislike toward particular people (Buss & nings (Insel et al., 2010). Durkee, 1957)], or acts of aggression (e.g., hitting To address this gap, we developed the Affective others or damaging property). Aggression and hos- Reactivity Index (ARI ), a scale that contains six tility may or may not occur with irritability. For symptom items and one impairment item about irri- example, irritability may be observable to the parent tability. We chose the item contents based on a simple, as the non-aggressive ‘huffing and puffing’ of a child broad definition of irritability as a mood of easy whose wish has been thwarted. To the child, irritable annoyance and touchiness characterized by anger mood may be present as a feeling that does not necessarily motivate aggressive action. Previous The scale’s initials are an anagram of ‘ira’, which is Latin for scales measuring irritability or trait anger frequently anger and rage. contain items of aggressive, antisocial, or hyperac- Conflict of interest statement: No conflicts declared. tive behavior and symptoms, such as ‘non-profitable Re-use of this article is permitted in accordance with the Terms damage to property’ (Vitiello, Behar, Hunt, Stoff, & and Conditions set out at http://wileyonlinelibrary.com/ Ricciuti, 1990), ‘I feel I might lose control and hit or onlineopen#OnlineOpen_Terms 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main St, Malden, MA 02148, USA 1110 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 hurt someone’ (Snaith & Taylor, 1985), ‘I attack Our second approach to testing the association of whatever makes me angry’ (Jacobs, Phelps, & Rohrs, the scale with psychopathology is applied to the UK 1989), ‘pick fights with anyone’, ‘just can’t sit still’ sample. We test the hypothesis that irritability will be (Mckinnie Burney, 2001), and ‘shout, kick, hit, let off differentially associated with emotional, rather than steam’ (Caprara et al., 1985). conduct or hyperactivity, symptoms. Theoretical In addition, the ARI was specifically designed to considerations (Burke, Loeber, Lahey, & Rathouz, obtain comparable information from youth and their 2005; Wakschlag, Tolan, & Leventhal, 2010) underlie parents. Some existing scales are available for ado- this hypothesis, as well as a host of recent evidence, lescent informants only (Del Barrio, Aluja, & Spiel- that irritability shows stronger associations with berger, 2004), which is a limitation when doing emotional problems, rather than conduct problems or research in developmental psychiatry (Angold, antisocial behaviors (Aebi et al., 2010; Rowe, Costello, 2002). Finally, the scale was specifically designed to Angold, Copeland, & Maughan, 2010; Stringaris, be (a) concise, which is in contrast to some of the Cohen, Pine, & Leibenluft, 2009; Stringaris & Good- existing scales (Buss & Durkee, 1957; Del Barrio man, 2009a,b). The scales used for this previous re- et al., 2004; Mckinnie Burney, 2001); (b) as simple search were generated ad hoc using items from as possible [e.g., avoid complex items such as ‘I feel existing instruments, rather than ones specifically infuriated when I do a good job and get poor evalu- designed, to measure irritability – these contained ation’ (Del Barrio et al., 2004) or ‘People pretend they only a few items and had low internal consistency are telling the truth, when they are really telling lies’ (Aebi et al., 2010; Stringaris & Goodman, 2009a,b). (Novaco & Taylor, 2004)]; (c) suitable for use as a Here, we test the hypothesis that irritability will screening instrument in busy clinics and epidemio- remain associated with emotional problems – but not logic studies. with conduct problems – when controlling for other This article reports the properties of the ARI in a variables such as hyperactivity, peer problems, or US- and a UK-sample. The first aim of this study was prosocial behaviors. to report item-level descriptive statistics. In this aim, we also sought to examine the internal consistencies Methods and test that a single-factor structure is appropriate in the two samples. As part of the first aim, we also The Affective Reactivity Index present preliminary data on the longitudinal stability The ARI was created as a parent- and a self-rated of the scale and compare the scale’s properties measure. Parents are presented with the following across a US and a UK sample. The second aim is to instruction sentence: ‘In the last 6 months and com- test the association of the scale with psychopathol- pared to others of the same age, how well does each of ogy, using two approaches. The first, undertaken in the following statements describe the behavior/feelings the US sample, compares four groups: healthy vol- of your child? Please try to answer all questions.’ The self-report version is identical apart from referring to unteers; unaffected children at family risk for BD, ‘your behaviour/feelings’). After the introduction, that is, those with a first degree relative diagnosed respondents are presented with six items related to with bipolar disorder (BD); children with BD; and feelings/behaviors specific for irritability (see Table 1), children with severe mood dysregulation [SMD; and one question assessing impairment due to irrita- (Leibenluft, 2011)]. Consistent with a dimensional bility (‘overall, irritability causes him/her (or ‘‘me’’ by view of irritability, we expect a graded increase of self-report) problems’). Each item has a three-level irritability from healthy volunteers through children response category: ‘not true’, ‘somewhat true’, ‘certainly at family risk for bipolar disorder and BD to SMD. true’ – scored as ‘0’, ‘1’, ‘2’, respectively, giving a range of We also test the hypothesis that the scale would possible scores of 0–12. Identical items comprise the distinguish between a group of patients selected for parent- and self-report scales. The total score is the irritability, that is, those with SMD, compared with sum of the first six items. The impairment item is not counted in the total score. The questionnaire was patients with other severe psychopathology, such as derived from a longer (21-item) version, designed to BD. This is important given the debate concerning contain redundancies. After piloting on 80 US cases the diagnostic boundaries of BD in youth. It had and controls, it was reduced according to aims about been claimed that severe irritability, even when it is coverage of duration, frequency, threshold (see Intro- not part of distinct episodes of altered mood, should duction), and parsimony (items that did not improve be considered a hallmark of pediatric BD (Spencer internal consistency or discrimination between cases et al., 2001; Wozniak et al., 1995). However, and controls were dropped). The ARI scales are copy- research on the SMD syndrome (Leibenluft, 2011; righted and available without charge from the first Leibenluft, Charney, Towbin, Bhangoo, & Pine, author. 2003), which is characterized by non-episodic severe irritability, suggests that SMD is unlikely to progress US sample to BD (Brotman et al., 2006; Stringaris et al., 2010), does not share family risk with BD (Brotman et al., This sample is part of an ongoing study at the National 2007), and has neural substrates separable from BD Institute of Mental Health (NIMH), which has been (Brotman et al., 2010). previously described (Brotman et al., 2007; Stringaris 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1111 Table 1 Mean scores and factor loadings for the ARI items across reporting source in the two samples US sample UK sample Mean (SD) Factor Factor Mean (SD) Factor Factor parent Mean (SD) Score Score parent Mean (SD) Score Score n = 214 self n = 194 parent self n =83 self n =50 parent self Easily annoyed by others 0.86 (0.82) 0.87 (0.70) 0.88 0.77 0.84 (0.77) 0.74 (0.69) 0.68 0.90 Often lose temper 0.72 (0.84) 0.62 (0.70) 0.96 0.91 0.69 (0.80) 0.62 (0.75) 0.97 0.96 Stay angry for a long time 0.38 (0.58) 0.37 (0.58) 0.81 0.72 0.49 (0.72) 0.52 (0.71) 0.81 0.78 Angry most of the time 0.29 (0.59) 0.18 (0.45) 0.89 0.81 0.16 (0.40) 0.30 (0.58) 0.82 0.88 Get angry frequently 0.63 (0.82) 0.48 (0.69) 0.97 0.92 0.51 (0.72) 0.46 (0.71) 0.97 0.94 Lose temper easily 0.76 (0.88) 0.61 (0.78) 0.97 0.98 0.65 (0.72) 0.68 (0.79) 0.97 0.93 CFI 0.99 1.00 1.00 0.99 TLI 1.00 1.00 1.00 0.98 RMSEA 0.05 0.09 0.00 0.21 WRMR 0.42 0.60 0.38 0.84 CFI, comparative fit index; RMSEA, root mean square error of approximation; TLI, Tucker Lewis Index; WRMR, weighted root mean square residual. et al., 2010). Here, we present data on those patients supplementary module (Leibenluft et al., 2003). Diag- who completed the ARI from March 2009 (when it was noses in the relatives of children at family risk for BD introduced) through August 2011. Patients with SMD, were confirmed by KSADS-PL(Kaufman et al., 1997) for or Bipolar Disorder Type I or Type II (BD), as well as child siblings with BD or, for parents or adult siblings children at family risk for BD were recruited through with BD, the Structured Clinical Interview for DSM- advertisements in support groups and with local psy- IV-TR Axis I Disorders-Patient Edition (SCID-I/P) (First, chiatrists, healthy volunteers were recruited through Spitzer, Gibbon, & Williams, 2002) or the Diagnostic advertisements. Details about the diagnoses of BD and Interview for Genetic Studies (DIGS) (Nurnberger et al., SMD can be found in the Appendix S1. 1994). KSADS-PL was also used to determine diagnoses There were 218 participants in the US sample of in the children at family risk for BD. whom 214 (98%) had ARI parent data, 194 (89%) had self-report data, and 192 (88%) had data by both Repeated ARI assessments reporting sources. The sample mean age was 12.90 years (SD = 2.70; range 6–17) with 130 (60%) A small fraction of participants (n = 19 by parent- boys. Diagnoses were: 67 (31%) with SMD, 39 (18%) report; n = 11 by self-report) completed the ARI twice as with BD, 35 (16%) children at family risk for BD (i.e., part of ongoing follow-up (M 1.12 years, SD 0.36). For first-degree BD relative), and 77 (35%) healthy volun- the participants who completed the ARI twice, we used teers. Data on comorbid diagnoses were available in all only the Time 1 data in the analyses described in the cases except: two cases with SMD, one case with BD, rest of this article. and two cases of children at family risk for BD. Of those with data on comorbidity, ADHD was also present in UK sample 55/65 (85%) of those with SMD and 32/38 (84%) of those with BD, while ODD was present in 54/65 (83%) The clinic sample (n = 34) consisted of patients, aged of those with SMD, and 16/38 (42%) of those with BD. 5–17 years, referred to the Community Child & Of the BD subjects, 25/38 (66%) of the BD patients Adolescent Mental Health Services of the South West were euthymic at assessment, while 11/38 (29%) were London & St Georges Mental Health NHS Trust. Par- hypomanic, 1/38 (3%) depressed, and 1/38 (3%) ticipation in the study was offered by the Specialist mixed. Further details about comorbidity and mood Registrar at the Service (co-author SF) to the patients state can be found in the Appendix S1. allocated to her. The most common diagnoses in the clinic sample were: ODD (15%, n = 5), ADHD (15%, n = 5), autism spectrum disorder (ASD, 9%, n = 3). Assessment of the US sample Also, 9% (n = 3) of cases presented with self-harm In addition to the measurement of irritability using the without a definite diagnosis. Only the primary diagnosis ARI, the Kiddie Schedule for Affective Disorders – provided by the Registrar was used in this study. Fur- Present and Lifetime Version (KSADS-PL) (Kaufman ther details of the sample are described in the Appendix et al., 1997) was administered to parents and children S1. separately by clinicians with graduate level training and The control sample (n = 54), consisting of participants established reliability (j = 0.9, including differentiating aged 6–18 years, was recruited from one primary school SMD and BD). Diagnoses were based on best-estimate and three secondary schools belonging to the same procedures (Leckman, Sholomskas, Thompson, Belan- geographical area as the clinic. The head teacher in ger, & Weissman, 1982), generated in a consensus each school was approached and written informed conference led by at least one psychiatrist with exten- consent was obtained for their school to participate in sive experience evaluating children with bipolar- the study. The head teacher then invited potential study spectrum illness. SMD was assessed using a KSADS participants by handing out the questionnaires and 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1112 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 consent forms to parents and young people in their reported irritability across healthy volunteers, children school. The questionnaires were handed to those fami- at family risk for bipolar disorder, BD, and SMD, with lies who were more likely to return completed ques- post hoc testing between groups. tionnaires as judged by the head teacher. The response In the UK sample, exploratory correlations were run rate from the primary school was 80%, while the aver- between irritability and scores on the SDQ subscales. age across the three secondary schools was 30%. Stu- To examine our hypothesis that irritability would be dents with severe intellectual disability were excluded. associated with emotional problems, rather than con- The control sample was assumed to have no psychiatric duct or antisocial disorders, a regression model was diagnosis. estimated. In this regression, the outcome variable was The mean age of the overall sample was 11.70 the emotional problems scale scores of the SDQ. The (SD = 3.46, range 5–18) with 59% (n = 52) boys. There total ARI score, as well as the hyperactivity, conduct, were no significant differences between the clinic and peer problems, and prosocial scale scores of the SDQ the community sample with regard to age and gender were entered as predictors all at once. Another regres- (see Appendix S1). sion model was also estimated with the conduct prob- ARI completion rates: of the 88 UK participants, 83 lems scale score of the SDQ as the outcome, and all (94%) had ARI parent data. Self-reported ARI was only previously mentioned scale scores were entered all at collected from children aged 11 and above: 52 children once as predictors (including the emotional problems in this sample were 11 years of age or older and self- scale score). Parent-reported outcomes were predicted report ARI data were available on 50 (96%) of them, by parent-reported variables; self-reported outcomes while 45 (87%) of them had data by both parent- and were predicted by self-reported variables. In addition, self-report. association between the total ARI score with the three levels (‘not true’, ‘somewhat true’, ‘certainly true’) of the impairment item (seventh ARI item) was tested using Assessment of the UK sample ANOVA in both samples. Each patient was assessed by a Specialty Registrar in Ethical approval US participants were enrolled in an Child and Adolescent psychiatry and diagnoses were Institutional Review Board approved study at the reviewed in multidisciplinary team meetings led by a Intramural Research Program of the National Institute senior psychiatrist. All UK participants completed the of Mental Health. Parents and children provided written Strengths and Difficulties Questionnaire (SDQ), but informed consent/assent. The UK study received were not assessed by a psychiatric interview. The SDQ approval from the East London Ethics Committee (10/ is a 25-item questionnaire with robust psychometric H0701/115). properties (Bourdon, Goodman, Rae, Simpson, & Koretz, 2005; Goodman, 2001) that generates dimen- sional scores for emotional, behavioral, hyperactivity, Results and peer problems, as well as prosocial behavior. All parents, and children aged 11 and above (52/88), were Aim 1: Descriptive statistics, internal reliability, asked to provide data. To avoid item (i.e., criterion) factorial structure, longitudinal stability, item overlap with the ARI, the temper tantrum item was comparison between reporters and relationship excluded from the behavioral scale for analyses (so the with age and gender sum of the rest of the conduct items was used instead). Item means and standard deviations for the whole sample are shown in Table 1. By either reporting Analyses All analyses were conducted separately by source, being easily annoyed by others was one of reporting source (parent- vs. self-report) and sample (US and UK). the most common items, whereas the two duration For our first aim, the means of items were calculated items, ‘stay angry for a long time’ and ‘angry most of for each sample. In addition, the single-factor structure the time’ were more rare. Total ARI scores by parent- of the ARI was tested in a confirmatory factor analysis. and self-report were higher for the US sample than This was conducted using the six ARI items in the US for the UK sample. In the US sample, Cronbach’s and the UK sample. Because of the categorical nature of alpha was 0.92 and 0.88 and in the UK sample 0.89 the items, weighted least square estimation was used as and 0.90, for the parent- and self-report scales, recommended (Yu, 2002). Fit was assessed on the basis respectively. of the following fit indices: Comparative Fit index (CFI; Table 1 shows the results of the confirmatory fac- 0.95 and above indicates good fit) the Tucker Lewis tor analysis: the CFI, TLI and WRMR all suggest that Index (TLI; values close to 1 indicate good fit) the root mean square error of approximation (RMSEA; values a one-factor solution is an adequate description of smaller than 0.05 indicate good fit), and the weighted the data. Only the RMSEA was higher than the rec- root mean square residual (WRMR; recommended cut- ommended benchmark for the self-reported scales. off at 0.6 (Yu, 2002). Internal consistency was esti- We compared, using repeated measures t-tests, mated using Cronbach’s alpha. Exploratory analyses the item means between parent- and self-report in for longitudinal stability were conducted using Pearson each sample (Table 2A,B). There are no statistically correlation coefficients. significant differences for any of the items in the Repeated measures t-tests were run in both samples UK sample. However, in the US sample, the to compare the item means between parent- and self- overall direction was for higher mean scores by reported data. The second aim was tested in the US parent-report, with four of six items being statisti- sample using ANOVA comparing parent- or self- 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1113 Table 2 (A) t-tests for individual items in the US sample. (B) t-tests for individual items in the UK sample Mean (SD) parent n = 192 Mean (SD) self n = 192 t-test statistics (df = 191) ns Easily annoyed by others 0.88 (0.83) 0.88 (0.70) t = 0.00 Often lose temper 0.76 (0.84) 0.61 (0.70) t = 2.64** ns Stay angry for a long time 0.39 (0.59) 0.38 (0.58) t = 0.31 Angry most of the time 0.30 (0.60) 0.18 (0.45) t = 2.50** Get angry frequently 0.67 (0.82) 0.48 (0.69) t = 3.03** Lose temper easily 0.79 (0.89) 0.61 (0.79) t = 3.03** Mean (SD) parent n = 45 Mean (SD) self n =45 t-test statistics (df = 44) ns Easily annoyed by others 0.82 (0.78) 0.73 (0.69) t = 1.07 ns Often lose temper 0.51 (0.76) 0.62 (0.75) t = )1.40 ns Stay angry for a long time 0.38 (0.65) 0.49 (0.73) t = )1.04 ns Angry most of the time 0.17 (0.44) 0.31 (0.60) t = )1.63 ns Get angry frequently 0.44 (0.69) 0.47 (0.69) t = )0.22 ns Lose temper easily 0.56 (0.69) 0.64 (0.77) t = )1.07 cally significantly higher by parent-report than by particular, SMD showed significantly more irritabil- self-report. ity than BD. By self-report, SMD and BD, but not Parent- and self-report scales were strongly and children at family risk for BD, showed significantly significantly correlated: r = 0.58 (CI 0.47–0.66) and more irritability than healthy volunteers. SMD also r = 0.73 (CI 0.56–0.85) for US and UK samples, reported more irritability than children at family risk respectively. In the US sample, there was no rela- for BD. The difference between SMD and BD was not tionship between age and either parent- (r = )0.06, significant by self-report. CI )0.19 to 0.08) or self-report ()0.10, CI )0.24 to 0.04) total score. In the UK sample, there was a Differential association of irritability Exploratory relationship between age and parent- (r = )0.26, CI univariate correlation analyses indicated that the )0.45 to )0.27) but not self-report (r = )0.12, CI ARI correlated with all SDQ subscales, with the )0.38 to 0.17) and ARI total score. exception of self-reported peer problems (Table 3). In In the US sample, by parent-report, there was no the univariate analyses, the association between difference in irritability levels between boys (3.66, irritability and emotional problems was comparable SD = 3.74) and girls (3.59, SD = 4.12), as assessed to the association between irritability and conduct by t-test (t = 0.12, df = 212, p = 0.91). There was problems by either reporting source: the confidence also no difference by self-report between boys (3.17, intervals of the correlation coefficients between ARI SD = 0.62) and girls (3.09, SD = 3.18), (t = 0.17, total score and emotional problems overlapped with df = 192, p = 0.86). the confidence intervals of the correlation coeffi- In the UK sample, by parent-report, there was no cients between ARI total score and conduct problems difference in irritability levels between boys (3.51, (Table 3). SD = 3.48) and girls (parent-report: 3.07, SD = 3.29), However, multivariate regression models show (t = 0.58, df = 81, p = 0.56). Also, by self-report, that, by parent-report, irritability was the sole there were no differences between boys (2.48, predictor of emotional problems (Table 4). By con- SD = 0.62) and girls (4.16, SD = 3.69), (t = 1.75, trast, hyperactivity was the sole predictor of con- df = 48, p = 0.09). duct problems (Table 4). By self-report, both The correlation coefficient for the longitudinal irritability and hyperactivity predicted emotional stability (over an average of about 1 year) was high problems and only irritability predicted conduct and significant by parent- (r = 0.88, p < 0.001), but problems. Note that parent-reported outcomes were not by self- report (r = 0.29, p = 0.28). predicted by parent-reported variables and self-re- ported outcomes were predicted by self-reported variables. Aim 2: Validation of scale Differences between healthy volunteers, children Associations between irritability symptoms and at family risk for BD, children with BD, and impairment due to irritability children with SMD in the US sample Figure 1A,B illustrates the gradation in irritability with lowest By either reporting source, increases in reported scores in healthy volunteers and highest scores in impairment were associated with significantly SMD, by either reporting source. By parent-report, increased irritability in both samples, with the all individual comparisons were significantly differ- exception of the difference between the intermediate ent, with the exception of that between healthy (a little) and top (a lot) category of impairment by self- volunteers and children at family risk for BD. In report, which was not significant (Appendix S1). 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1114 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 sample, they were significantly higher by parent- (A) compared to self-report for most items in the US Mean ARI score (95% CI) by diagnostic group parent rated sample. The higher severity of irritability in the specialized US sample may underlie these differ- ences. The ARI items showed excellent internal consistency and good factorial structure – only by self-report did one of the four indices, the RMSEA, not suggest an optimal fit. These results demon- strate the utility of the ARI across clinic and com- 0 munity-based samples in two countries and across HV (n = 76) FRBD (n = 35) BD (n = 39) SMD (n = 64) informants, suggesting that the scale can be used transnationally. The longitudinal stability of the ARI F (210, 3) = 96.34 F-test p<0.001 seems promising (at least by parent-report), al- ns HV vs. FRBD *** though this inference was drawn using a very small HV < BD *** Sheffe HV < SMD subsample and will require replication. *** FRBD < BD Post hoc *** FRBD < SMD Our second aim was to examine how the scale is ** BD < SMD associated with psychopathology. In the US sample, by parent-report, irritability was highest in SMD (B) compared with healthy volunteers, children at family Mean ARI score (95% CI) by diagnostic group risk for bipolar disorder, and BD. However, irritability self rated in BD was higher than in healthy volunteers or in 6 children at family risk for BD. By self-report, how- ever, differences in irritability between SMD and BD were non-significant, indicating that youth-report is less good at differentiating between these pheno- types. These results highlight the fact that a high level of chronic irritability, while a defining feature of SMD (Leibenluft et al., 2003), may also occur in children HV (n = 64) FRBD (n = 29) BD (n = 36) SMD (n = 65) with BD. It should also be noted that the BD pheno- type examined here is designed to be narrow, that is, F(190,3) = 20.85 F-test p<0.001 to only include children with elated or expansive ns HV vs FRBD *** mood, who may or may not also have irritability, but HV < BD *** Sheffe HV < SMD not the rare group of children (Hunt et al., 2009) ns FRBD < BD Post hoc *** presenting with episodic irritability only. FRBD < SMD ns BD < SMD In keeping with our hypothesis (Stringaris & Goodman, 2009a,b), parent-reported irritability was Figure 1 (A) Mean ARI score (95% CI) by diagnostic group par- the only predictor of emotional problems when com- ent-rated. ‘ns’ denotes no statistically significant differences, sample sizes reflect those with parent-report ARI data avail- pared with all other SDQ subscales in multivariate able.***p < 0.001, **p < 0.01. HV, healthy volunteers. FRBD, models; conversely, only hyperactivity, but not irri- children at family risk for bipolar disorder. BD, children with tability, predicted conduct problems. However, by bipolar disorder. SMD, severe mood dysregulation. (B) Mean ARI self-report, irritability and self-reported hyperactivity score (95% CI) by diagnostic group self-rated. ‘ns’ denotes no problems predicted emotional problems, and self-re- statistically significant differences, sample sizes reflect those with ported irritability also strongly predicted self-reported self-report ARI data available.***p < 0.001, **p < 0.01. HV, healthy volunteers. FRBD, children at family risk for bipolar dis- conduct problems. It should also be noted that in the order. BD, children with bipolar disorder. SMD, severe mood univariate analyses, irritability was related to either dysregulation emotional or conduct problems, by either reporting source. This suggests that irritability in this age group acts as an indicator of either conduct or emotional Discussion problems. As previously suggested (Stringaris, Zavos, This article reports on the characteristics of the ARI, Leibenluft, Maughan, & Eley, 2011), this relationship a concise parent- and self-reported questionnaire between irritability and conduct problems may itself designed to assess youth irritability. be mediated through headstrong and hurtful behav- Our first aim was to describe the basic character- iors, which were not controlled here. A related, but not istics of the scale in the US and UK samples. We identical, dimension of negative affect has been re- found a similar pattern of item frequencies across cently identified as part of oppositional problems reporting sources and samples, although the abso- (Burke, Hipwell, & Loeber, 2010). lute frequencies of the items varied. The two items on This study’s strengths include the use of samples prolonged anger were endorsed least often. More- across two countries spanning a number of diagnoses over, we found that while the item means between and ascertainment methods, and the comparison reporting sources were very similar in the UK between SMD and BD. However, it also has a number 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1115 Table 3 Pearson correlations (and 95% confidence intervals) between ARI and other SDQ scores. Parent-report is above and self- report below the diagonal (UK sample) Irritability Emotional Conduct Hyperactivity Peer Prosocial (ARI) (SDQ) (SDQ) (SDQ) (SDQ) (SDQ) Irritability (ARI) – 0.60 0.55 0.33 0.23 )0.55 (0.39 to 0.75) (0.31 to 0.72) (0.05 to 0.56) ()0.06 to 0.49) ()0.72 to )0.31) Emotional (SDQ) 0.66 – 0.36 0.48 0.28 )0.37 (0.52 to 0.77) (0.08 to 0.58) (0.23 to 0.67) ()0.00 to 0.53) ()0.59 to )0.09) ns Conduct (SDQ) 0.48 0.43 – 0.29 0.32 )0.21 (0.29 to 0.63) (0.24 to 0.59) (0.00 to 0.53) (0.04 to 0.55) ()0.46 to 0.08) ns ns Hyperactivity (SDQ) 0.39 0.38 0.49 – 0.04 )0.04 (0.19 to 0.56) (0.18 to 0.55) (0.30 to 0.64) ()0.24 to 0.32) ()0.32 to 0.25) ns Peer (SDQ) 0.30 0.38 0.28 0.25 – )0.06 (0.09 to 0.48) (0.18 to 0.55) (0.07 to 0.47) (0.03 to 0.44) ()0.22 to 0.34) ns Prosocial (SDQ) )0.57 )0.24 )0.21 )0.13 0.03 – ()0.67 to )0.36) ()0.43 to )0.02) ()0.41 to 0.00) ()0.33 to 0.09) ()0.24 to 0.19) ARI, Affective Reactivity Index; SDQ, Strengths and Difficulties Questionnaire. Parent-report n = 82 (one subject with ARI but no SDQ data); self-report: n = 48 (two subjects with ARI but no SDQ data). Table 4 Association between irritability, conduct, and emotion problems in the UK sample Outcomes Parent n = 81 Self n =48 Predictors Emotional (SDQ) Conduct (SDQ) Emotional (SDQ) Conduct (SDQ) Irritability (ARI) 0.61*** (0.38 to 0.84) 0.35 ()0.07 to 0.78) 0.36* (0.04 to 0.68) 0.63** (0.18 to 1.07) Hyperactivity (SDQ) 0.10 ()0.10 to 0.30) 0.50** (0.20 to 0.81) 0.36** (0.11 to 0.60) 0.18 ()0.20 to 0.55) Conduct (SDQ) 0.06 ()0.08 to 0.20) n/a )0.04 ().26 to 0.18) n/a Emotional (SDQ) n/a 0.15 ()022 to 0.52) n/a )0.08 ()052 to 0.37) Peer (SDQ) 0.15 ()0.03 to 0.33) 0.09 ()0.20 to 0.38) 0.21 ()0.03 to 0.45) 0.27 ()0.08 to 0.61) Prosocial (SDQ) 0.11 ()0.08 to 0.31) )0.02 ()0.34 to 0.30) )0.18 ()0.45 to 0.10) 0.04 ()0.36 to 0.45) ARI, Affective Reactivity Index; SDQ, Strengths and Difficulties Questionnaire. Beta coefficients (and confidence intervals) are reported from linear regression models; ***p < 0.001, **p < 0.01, *p < 0.05. Parent- reported outcomes were predicted by parent-reported variables and self-reported outcomes were predicted by self-reported variables. of weaknesses. First, the samples are subject to assess the importance of irritability to psychopa- referral and Berkson bias, limitations common to all thology. clinic-based studies (Caron & Rutter, 1991). To address this, the ARI should be validated in epidemi- Acknowledgements ologic samples. Second, the size of the UK sample is The authors have declared that they have no competing small. Future studies with larger numbers should be or potential conflicts of interest. This manuscript is conducted to examine how irritability predicts, for based on material funded by the Wellcome Trust. Argyris Stringaris gratefully acknowledges the support example, treatment outcomes in clinics. Third, the of the Wellcome Trust. cross-sectional nature of our main results limits the inferences that can be drawn. Fourth, this scale was not designed as an in-depth probe of the phenome- Correspondence to nology of irritability or of its relationship with pheno- Argyris Stringaris, King’s College London, Institute of types of more general emotional and behavioral Psychiatry, Denmark Hill, London, SE5 8AF, UK; dyscontrol (Holtmann et al., 2010). Further research Email: [email protected] is needed to understand these relationships. Also, the ARI was developed to capture irritability in a way that would be accessible to participants from as wide a Supporting information child age-range as possible. Future research should Additional supporting information is provided along determine whether it could also be used for adult self- with the online version of this article. report of irritability. Appendix S1: The Affective Reactivity Index. In conclusion, the ARI demonstrates promising Please note: Wiley-Blackwell are not responsible for psychometric properties and it may prove a useful the content or functionality of any supporting materials supplied by the authors. Any queries (other than tool for clinical and research purposes. Future missing material) should be directed to the corre- epidemiologic samples and clinic samples with sponding author for the article. treatment designs using the ARI may further 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1116 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 Key points • Irritability is a form of mood dysregulation of intense scientific interest. • The Affective Reactivity Index is a concise (seven item) scale for the dimensional measurement of irritability. • The ARI has excellent internal consistency and forms a single factor in both parent- and self-report forms. • The parent- and self-reported ARI total score differentiates cases from controls in a clinic and a community sample. The parent-rated ARI total score also differentiates between youth with severe mood dysregulation and youth with bipolar disorder. • The ARI may be a useful tool for the measurement of irritability. Buss, A.H., & Durkee, A. (1957). An inventory for assesssing References different kinds of hostility. Journal of Consulting Psychology, Aebi, M., Asherson, P., Banaschewski, T., Buitelaar, J., 21, 343–349. 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Journal of the American Academy of Child and Published online: 10 May 2012 Adolescent Psychiatry, 49, 397–405. 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Child Psychology and Psychiatry, and Allied Disciplines Pubmed Central

The Affective Reactivity Index: a concise irritability scale for clinical and research settings

Stringaris, Argyris; Goodman, Robert; Ferdinando, Sumudu; Razdan, Varun; Muhrer, Eli; Leibenluft, Ellen; Brotman, Melissa A
Journal of Child Psychology and Psychiatry, and Allied Disciplines , Volume 53 (11) – Nov 1, 2012
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Journal of Child Psychology and Psychiatry 53:11 (2012), pp 1109–1117 doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index: a concise irritability scale for clinical and research settings 1 1 1 2 Argyris Stringaris , Robert Goodman , Sumudu Ferdinando , Varun Razdan , 2 2 2 Eli Muhrer , Ellen Leibenluft and Melissa A. Brotman King’s College London, Institute of Psychiatry, Denmark Hill, London, UK Section on Bipolar Spectrum Disorders, Emotion and Development Branch, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD USA Background: Irritable mood has recently become a matter of intense scientific interest. Here, we present data from two samples, one from the United States and the other from the United Kingdom, demon- strating the clinical and research utility of the parent- and self-report forms of the Affective Reactivity Index (ARI), a concise dimensional measure of irritability. Methods: The US sample (n = 218) consisted of children and adolescents recruited at the National Institute of Mental Health meeting criteria for bipolar disorder (BD, n = 39), severe mood dysregulation (SMD, n = 67), children at family risk for BD (n = 35), or were healthy volunteers (n = 77). The UK sample (n = 88) was comprised of children from a generic mental health setting and healthy volunteers from primary and secondary schools. Results: Parent- and self- report scales of the ARI showed excellent internal consistencies and formed a single factor in the two samples. In the US sample, the ARI showed a gradation with irritability significantly increasing from healthy volunteers through to SMD. Irritability was significantly higher in SMD than in BD by parent- report, but this did not reach significance by self-report. In the UK sample, parent-rated irritability was differentially related to emotional problems. Conclusions: Irritability can be measured using a concise instrument both in a highly specialized US, as well as a general UK child mental health setting. Keywords: Mood dysregulation, Affective Reactivity Index, irritability, depression, bipolar and temper outbursts (Stringaris, 2011). Respon- Introduction dents rate irritability over the last 6 months. The scale Recently, irritable mood has become a focus of in- focuses on chronic irritability (Leibenluft, Cohen, tense scientific interest (Leibenluft, 2011; Stringaris, Gorrindo, Brook, & Pine, 2006). This presents com- 2011). However, research on the measurement of monly as a child who is described by his/her parents irritability has been limited. This study reports the as ‘always angry’ and as reacting with intense anger to psychometric properties of a concise irritability situations that other children would take in their measure for use in clinical practice and research. stride. This differs from the less usual presentation of While irritability is listed as a symptom for multi- irritability occurring as part of a circumscribed epi- ple diagnoses, the term is not defined in the DSM-IV sode (APA, 2000; Leibenluft et al., 2006). (APA, 2000), and there is no consensus definition in Specifically, the ARI scale was designed to exam- the literature. Moreover, despite the intense interest ine, in a way accessible to most children and par- of the DSM-5 taskforce in irritability, defined both ents, three aspects of irritability: (a) threshold for an dimensionally and categorically (APA, 2011a,b), angry reaction; (b) frequency of angry feelings/ research on the measurement of irritability has been behaviors; (c) duration of such feelings/behaviors. limited. This is unfortunate, given the importance The scale was designed to ascertain irritable mood ascribed to studying the dimensional structure of rather than its possible consequences such as hos- psychopathology and its neurobiological underpin- tility [i.e., dislike toward particular people (Buss & nings (Insel et al., 2010). Durkee, 1957)], or acts of aggression (e.g., hitting To address this gap, we developed the Affective others or damaging property). Aggression and hos- Reactivity Index (ARI ), a scale that contains six tility may or may not occur with irritability. For symptom items and one impairment item about irri- example, irritability may be observable to the parent tability. We chose the item contents based on a simple, as the non-aggressive ‘huffing and puffing’ of a child broad definition of irritability as a mood of easy whose wish has been thwarted. To the child, irritable annoyance and touchiness characterized by anger mood may be present as a feeling that does not necessarily motivate aggressive action. Previous The scale’s initials are an anagram of ‘ira’, which is Latin for scales measuring irritability or trait anger frequently anger and rage. contain items of aggressive, antisocial, or hyperac- Conflict of interest statement: No conflicts declared. tive behavior and symptoms, such as ‘non-profitable Re-use of this article is permitted in accordance with the Terms damage to property’ (Vitiello, Behar, Hunt, Stoff, & and Conditions set out at http://wileyonlinelibrary.com/ Ricciuti, 1990), ‘I feel I might lose control and hit or onlineopen#OnlineOpen_Terms 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main St, Malden, MA 02148, USA 1110 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 hurt someone’ (Snaith & Taylor, 1985), ‘I attack Our second approach to testing the association of whatever makes me angry’ (Jacobs, Phelps, & Rohrs, the scale with psychopathology is applied to the UK 1989), ‘pick fights with anyone’, ‘just can’t sit still’ sample. We test the hypothesis that irritability will be (Mckinnie Burney, 2001), and ‘shout, kick, hit, let off differentially associated with emotional, rather than steam’ (Caprara et al., 1985). conduct or hyperactivity, symptoms. Theoretical In addition, the ARI was specifically designed to considerations (Burke, Loeber, Lahey, & Rathouz, obtain comparable information from youth and their 2005; Wakschlag, Tolan, & Leventhal, 2010) underlie parents. Some existing scales are available for ado- this hypothesis, as well as a host of recent evidence, lescent informants only (Del Barrio, Aluja, & Spiel- that irritability shows stronger associations with berger, 2004), which is a limitation when doing emotional problems, rather than conduct problems or research in developmental psychiatry (Angold, antisocial behaviors (Aebi et al., 2010; Rowe, Costello, 2002). Finally, the scale was specifically designed to Angold, Copeland, & Maughan, 2010; Stringaris, be (a) concise, which is in contrast to some of the Cohen, Pine, & Leibenluft, 2009; Stringaris & Good- existing scales (Buss & Durkee, 1957; Del Barrio man, 2009a,b). The scales used for this previous re- et al., 2004; Mckinnie Burney, 2001); (b) as simple search were generated ad hoc using items from as possible [e.g., avoid complex items such as ‘I feel existing instruments, rather than ones specifically infuriated when I do a good job and get poor evalu- designed, to measure irritability – these contained ation’ (Del Barrio et al., 2004) or ‘People pretend they only a few items and had low internal consistency are telling the truth, when they are really telling lies’ (Aebi et al., 2010; Stringaris & Goodman, 2009a,b). (Novaco & Taylor, 2004)]; (c) suitable for use as a Here, we test the hypothesis that irritability will screening instrument in busy clinics and epidemio- remain associated with emotional problems – but not logic studies. with conduct problems – when controlling for other This article reports the properties of the ARI in a variables such as hyperactivity, peer problems, or US- and a UK-sample. The first aim of this study was prosocial behaviors. to report item-level descriptive statistics. In this aim, we also sought to examine the internal consistencies Methods and test that a single-factor structure is appropriate in the two samples. As part of the first aim, we also The Affective Reactivity Index present preliminary data on the longitudinal stability The ARI was created as a parent- and a self-rated of the scale and compare the scale’s properties measure. Parents are presented with the following across a US and a UK sample. The second aim is to instruction sentence: ‘In the last 6 months and com- test the association of the scale with psychopathol- pared to others of the same age, how well does each of ogy, using two approaches. The first, undertaken in the following statements describe the behavior/feelings the US sample, compares four groups: healthy vol- of your child? Please try to answer all questions.’ The self-report version is identical apart from referring to unteers; unaffected children at family risk for BD, ‘your behaviour/feelings’). After the introduction, that is, those with a first degree relative diagnosed respondents are presented with six items related to with bipolar disorder (BD); children with BD; and feelings/behaviors specific for irritability (see Table 1), children with severe mood dysregulation [SMD; and one question assessing impairment due to irrita- (Leibenluft, 2011)]. Consistent with a dimensional bility (‘overall, irritability causes him/her (or ‘‘me’’ by view of irritability, we expect a graded increase of self-report) problems’). Each item has a three-level irritability from healthy volunteers through children response category: ‘not true’, ‘somewhat true’, ‘certainly at family risk for bipolar disorder and BD to SMD. true’ – scored as ‘0’, ‘1’, ‘2’, respectively, giving a range of We also test the hypothesis that the scale would possible scores of 0–12. Identical items comprise the distinguish between a group of patients selected for parent- and self-report scales. The total score is the irritability, that is, those with SMD, compared with sum of the first six items. The impairment item is not counted in the total score. The questionnaire was patients with other severe psychopathology, such as derived from a longer (21-item) version, designed to BD. This is important given the debate concerning contain redundancies. After piloting on 80 US cases the diagnostic boundaries of BD in youth. It had and controls, it was reduced according to aims about been claimed that severe irritability, even when it is coverage of duration, frequency, threshold (see Intro- not part of distinct episodes of altered mood, should duction), and parsimony (items that did not improve be considered a hallmark of pediatric BD (Spencer internal consistency or discrimination between cases et al., 2001; Wozniak et al., 1995). However, and controls were dropped). The ARI scales are copy- research on the SMD syndrome (Leibenluft, 2011; righted and available without charge from the first Leibenluft, Charney, Towbin, Bhangoo, & Pine, author. 2003), which is characterized by non-episodic severe irritability, suggests that SMD is unlikely to progress US sample to BD (Brotman et al., 2006; Stringaris et al., 2010), does not share family risk with BD (Brotman et al., This sample is part of an ongoing study at the National 2007), and has neural substrates separable from BD Institute of Mental Health (NIMH), which has been (Brotman et al., 2010). previously described (Brotman et al., 2007; Stringaris 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1111 Table 1 Mean scores and factor loadings for the ARI items across reporting source in the two samples US sample UK sample Mean (SD) Factor Factor Mean (SD) Factor Factor parent Mean (SD) Score Score parent Mean (SD) Score Score n = 214 self n = 194 parent self n =83 self n =50 parent self Easily annoyed by others 0.86 (0.82) 0.87 (0.70) 0.88 0.77 0.84 (0.77) 0.74 (0.69) 0.68 0.90 Often lose temper 0.72 (0.84) 0.62 (0.70) 0.96 0.91 0.69 (0.80) 0.62 (0.75) 0.97 0.96 Stay angry for a long time 0.38 (0.58) 0.37 (0.58) 0.81 0.72 0.49 (0.72) 0.52 (0.71) 0.81 0.78 Angry most of the time 0.29 (0.59) 0.18 (0.45) 0.89 0.81 0.16 (0.40) 0.30 (0.58) 0.82 0.88 Get angry frequently 0.63 (0.82) 0.48 (0.69) 0.97 0.92 0.51 (0.72) 0.46 (0.71) 0.97 0.94 Lose temper easily 0.76 (0.88) 0.61 (0.78) 0.97 0.98 0.65 (0.72) 0.68 (0.79) 0.97 0.93 CFI 0.99 1.00 1.00 0.99 TLI 1.00 1.00 1.00 0.98 RMSEA 0.05 0.09 0.00 0.21 WRMR 0.42 0.60 0.38 0.84 CFI, comparative fit index; RMSEA, root mean square error of approximation; TLI, Tucker Lewis Index; WRMR, weighted root mean square residual. et al., 2010). Here, we present data on those patients supplementary module (Leibenluft et al., 2003). Diag- who completed the ARI from March 2009 (when it was noses in the relatives of children at family risk for BD introduced) through August 2011. Patients with SMD, were confirmed by KSADS-PL(Kaufman et al., 1997) for or Bipolar Disorder Type I or Type II (BD), as well as child siblings with BD or, for parents or adult siblings children at family risk for BD were recruited through with BD, the Structured Clinical Interview for DSM- advertisements in support groups and with local psy- IV-TR Axis I Disorders-Patient Edition (SCID-I/P) (First, chiatrists, healthy volunteers were recruited through Spitzer, Gibbon, & Williams, 2002) or the Diagnostic advertisements. Details about the diagnoses of BD and Interview for Genetic Studies (DIGS) (Nurnberger et al., SMD can be found in the Appendix S1. 1994). KSADS-PL was also used to determine diagnoses There were 218 participants in the US sample of in the children at family risk for BD. whom 214 (98%) had ARI parent data, 194 (89%) had self-report data, and 192 (88%) had data by both Repeated ARI assessments reporting sources. The sample mean age was 12.90 years (SD = 2.70; range 6–17) with 130 (60%) A small fraction of participants (n = 19 by parent- boys. Diagnoses were: 67 (31%) with SMD, 39 (18%) report; n = 11 by self-report) completed the ARI twice as with BD, 35 (16%) children at family risk for BD (i.e., part of ongoing follow-up (M 1.12 years, SD 0.36). For first-degree BD relative), and 77 (35%) healthy volun- the participants who completed the ARI twice, we used teers. Data on comorbid diagnoses were available in all only the Time 1 data in the analyses described in the cases except: two cases with SMD, one case with BD, rest of this article. and two cases of children at family risk for BD. Of those with data on comorbidity, ADHD was also present in UK sample 55/65 (85%) of those with SMD and 32/38 (84%) of those with BD, while ODD was present in 54/65 (83%) The clinic sample (n = 34) consisted of patients, aged of those with SMD, and 16/38 (42%) of those with BD. 5–17 years, referred to the Community Child & Of the BD subjects, 25/38 (66%) of the BD patients Adolescent Mental Health Services of the South West were euthymic at assessment, while 11/38 (29%) were London & St Georges Mental Health NHS Trust. Par- hypomanic, 1/38 (3%) depressed, and 1/38 (3%) ticipation in the study was offered by the Specialist mixed. Further details about comorbidity and mood Registrar at the Service (co-author SF) to the patients state can be found in the Appendix S1. allocated to her. The most common diagnoses in the clinic sample were: ODD (15%, n = 5), ADHD (15%, n = 5), autism spectrum disorder (ASD, 9%, n = 3). Assessment of the US sample Also, 9% (n = 3) of cases presented with self-harm In addition to the measurement of irritability using the without a definite diagnosis. Only the primary diagnosis ARI, the Kiddie Schedule for Affective Disorders – provided by the Registrar was used in this study. Fur- Present and Lifetime Version (KSADS-PL) (Kaufman ther details of the sample are described in the Appendix et al., 1997) was administered to parents and children S1. separately by clinicians with graduate level training and The control sample (n = 54), consisting of participants established reliability (j = 0.9, including differentiating aged 6–18 years, was recruited from one primary school SMD and BD). Diagnoses were based on best-estimate and three secondary schools belonging to the same procedures (Leckman, Sholomskas, Thompson, Belan- geographical area as the clinic. The head teacher in ger, & Weissman, 1982), generated in a consensus each school was approached and written informed conference led by at least one psychiatrist with exten- consent was obtained for their school to participate in sive experience evaluating children with bipolar- the study. The head teacher then invited potential study spectrum illness. SMD was assessed using a KSADS participants by handing out the questionnaires and 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1112 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 consent forms to parents and young people in their reported irritability across healthy volunteers, children school. The questionnaires were handed to those fami- at family risk for bipolar disorder, BD, and SMD, with lies who were more likely to return completed ques- post hoc testing between groups. tionnaires as judged by the head teacher. The response In the UK sample, exploratory correlations were run rate from the primary school was 80%, while the aver- between irritability and scores on the SDQ subscales. age across the three secondary schools was 30%. Stu- To examine our hypothesis that irritability would be dents with severe intellectual disability were excluded. associated with emotional problems, rather than con- The control sample was assumed to have no psychiatric duct or antisocial disorders, a regression model was diagnosis. estimated. In this regression, the outcome variable was The mean age of the overall sample was 11.70 the emotional problems scale scores of the SDQ. The (SD = 3.46, range 5–18) with 59% (n = 52) boys. There total ARI score, as well as the hyperactivity, conduct, were no significant differences between the clinic and peer problems, and prosocial scale scores of the SDQ the community sample with regard to age and gender were entered as predictors all at once. Another regres- (see Appendix S1). sion model was also estimated with the conduct prob- ARI completion rates: of the 88 UK participants, 83 lems scale score of the SDQ as the outcome, and all (94%) had ARI parent data. Self-reported ARI was only previously mentioned scale scores were entered all at collected from children aged 11 and above: 52 children once as predictors (including the emotional problems in this sample were 11 years of age or older and self- scale score). Parent-reported outcomes were predicted report ARI data were available on 50 (96%) of them, by parent-reported variables; self-reported outcomes while 45 (87%) of them had data by both parent- and were predicted by self-reported variables. In addition, self-report. association between the total ARI score with the three levels (‘not true’, ‘somewhat true’, ‘certainly true’) of the impairment item (seventh ARI item) was tested using Assessment of the UK sample ANOVA in both samples. Each patient was assessed by a Specialty Registrar in Ethical approval US participants were enrolled in an Child and Adolescent psychiatry and diagnoses were Institutional Review Board approved study at the reviewed in multidisciplinary team meetings led by a Intramural Research Program of the National Institute senior psychiatrist. All UK participants completed the of Mental Health. Parents and children provided written Strengths and Difficulties Questionnaire (SDQ), but informed consent/assent. The UK study received were not assessed by a psychiatric interview. The SDQ approval from the East London Ethics Committee (10/ is a 25-item questionnaire with robust psychometric H0701/115). properties (Bourdon, Goodman, Rae, Simpson, & Koretz, 2005; Goodman, 2001) that generates dimen- sional scores for emotional, behavioral, hyperactivity, Results and peer problems, as well as prosocial behavior. All parents, and children aged 11 and above (52/88), were Aim 1: Descriptive statistics, internal reliability, asked to provide data. To avoid item (i.e., criterion) factorial structure, longitudinal stability, item overlap with the ARI, the temper tantrum item was comparison between reporters and relationship excluded from the behavioral scale for analyses (so the with age and gender sum of the rest of the conduct items was used instead). Item means and standard deviations for the whole sample are shown in Table 1. By either reporting Analyses All analyses were conducted separately by source, being easily annoyed by others was one of reporting source (parent- vs. self-report) and sample (US and UK). the most common items, whereas the two duration For our first aim, the means of items were calculated items, ‘stay angry for a long time’ and ‘angry most of for each sample. In addition, the single-factor structure the time’ were more rare. Total ARI scores by parent- of the ARI was tested in a confirmatory factor analysis. and self-report were higher for the US sample than This was conducted using the six ARI items in the US for the UK sample. In the US sample, Cronbach’s and the UK sample. Because of the categorical nature of alpha was 0.92 and 0.88 and in the UK sample 0.89 the items, weighted least square estimation was used as and 0.90, for the parent- and self-report scales, recommended (Yu, 2002). Fit was assessed on the basis respectively. of the following fit indices: Comparative Fit index (CFI; Table 1 shows the results of the confirmatory fac- 0.95 and above indicates good fit) the Tucker Lewis tor analysis: the CFI, TLI and WRMR all suggest that Index (TLI; values close to 1 indicate good fit) the root mean square error of approximation (RMSEA; values a one-factor solution is an adequate description of smaller than 0.05 indicate good fit), and the weighted the data. Only the RMSEA was higher than the rec- root mean square residual (WRMR; recommended cut- ommended benchmark for the self-reported scales. off at 0.6 (Yu, 2002). Internal consistency was esti- We compared, using repeated measures t-tests, mated using Cronbach’s alpha. Exploratory analyses the item means between parent- and self-report in for longitudinal stability were conducted using Pearson each sample (Table 2A,B). There are no statistically correlation coefficients. significant differences for any of the items in the Repeated measures t-tests were run in both samples UK sample. However, in the US sample, the to compare the item means between parent- and self- overall direction was for higher mean scores by reported data. The second aim was tested in the US parent-report, with four of six items being statisti- sample using ANOVA comparing parent- or self- 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1113 Table 2 (A) t-tests for individual items in the US sample. (B) t-tests for individual items in the UK sample Mean (SD) parent n = 192 Mean (SD) self n = 192 t-test statistics (df = 191) ns Easily annoyed by others 0.88 (0.83) 0.88 (0.70) t = 0.00 Often lose temper 0.76 (0.84) 0.61 (0.70) t = 2.64** ns Stay angry for a long time 0.39 (0.59) 0.38 (0.58) t = 0.31 Angry most of the time 0.30 (0.60) 0.18 (0.45) t = 2.50** Get angry frequently 0.67 (0.82) 0.48 (0.69) t = 3.03** Lose temper easily 0.79 (0.89) 0.61 (0.79) t = 3.03** Mean (SD) parent n = 45 Mean (SD) self n =45 t-test statistics (df = 44) ns Easily annoyed by others 0.82 (0.78) 0.73 (0.69) t = 1.07 ns Often lose temper 0.51 (0.76) 0.62 (0.75) t = )1.40 ns Stay angry for a long time 0.38 (0.65) 0.49 (0.73) t = )1.04 ns Angry most of the time 0.17 (0.44) 0.31 (0.60) t = )1.63 ns Get angry frequently 0.44 (0.69) 0.47 (0.69) t = )0.22 ns Lose temper easily 0.56 (0.69) 0.64 (0.77) t = )1.07 cally significantly higher by parent-report than by particular, SMD showed significantly more irritabil- self-report. ity than BD. By self-report, SMD and BD, but not Parent- and self-report scales were strongly and children at family risk for BD, showed significantly significantly correlated: r = 0.58 (CI 0.47–0.66) and more irritability than healthy volunteers. SMD also r = 0.73 (CI 0.56–0.85) for US and UK samples, reported more irritability than children at family risk respectively. In the US sample, there was no rela- for BD. The difference between SMD and BD was not tionship between age and either parent- (r = )0.06, significant by self-report. CI )0.19 to 0.08) or self-report ()0.10, CI )0.24 to 0.04) total score. In the UK sample, there was a Differential association of irritability Exploratory relationship between age and parent- (r = )0.26, CI univariate correlation analyses indicated that the )0.45 to )0.27) but not self-report (r = )0.12, CI ARI correlated with all SDQ subscales, with the )0.38 to 0.17) and ARI total score. exception of self-reported peer problems (Table 3). In In the US sample, by parent-report, there was no the univariate analyses, the association between difference in irritability levels between boys (3.66, irritability and emotional problems was comparable SD = 3.74) and girls (3.59, SD = 4.12), as assessed to the association between irritability and conduct by t-test (t = 0.12, df = 212, p = 0.91). There was problems by either reporting source: the confidence also no difference by self-report between boys (3.17, intervals of the correlation coefficients between ARI SD = 0.62) and girls (3.09, SD = 3.18), (t = 0.17, total score and emotional problems overlapped with df = 192, p = 0.86). the confidence intervals of the correlation coeffi- In the UK sample, by parent-report, there was no cients between ARI total score and conduct problems difference in irritability levels between boys (3.51, (Table 3). SD = 3.48) and girls (parent-report: 3.07, SD = 3.29), However, multivariate regression models show (t = 0.58, df = 81, p = 0.56). Also, by self-report, that, by parent-report, irritability was the sole there were no differences between boys (2.48, predictor of emotional problems (Table 4). By con- SD = 0.62) and girls (4.16, SD = 3.69), (t = 1.75, trast, hyperactivity was the sole predictor of con- df = 48, p = 0.09). duct problems (Table 4). By self-report, both The correlation coefficient for the longitudinal irritability and hyperactivity predicted emotional stability (over an average of about 1 year) was high problems and only irritability predicted conduct and significant by parent- (r = 0.88, p < 0.001), but problems. Note that parent-reported outcomes were not by self- report (r = 0.29, p = 0.28). predicted by parent-reported variables and self-re- ported outcomes were predicted by self-reported variables. Aim 2: Validation of scale Differences between healthy volunteers, children Associations between irritability symptoms and at family risk for BD, children with BD, and impairment due to irritability children with SMD in the US sample Figure 1A,B illustrates the gradation in irritability with lowest By either reporting source, increases in reported scores in healthy volunteers and highest scores in impairment were associated with significantly SMD, by either reporting source. By parent-report, increased irritability in both samples, with the all individual comparisons were significantly differ- exception of the difference between the intermediate ent, with the exception of that between healthy (a little) and top (a lot) category of impairment by self- volunteers and children at family risk for BD. In report, which was not significant (Appendix S1). 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1114 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 sample, they were significantly higher by parent- (A) compared to self-report for most items in the US Mean ARI score (95% CI) by diagnostic group parent rated sample. The higher severity of irritability in the specialized US sample may underlie these differ- ences. The ARI items showed excellent internal consistency and good factorial structure – only by self-report did one of the four indices, the RMSEA, not suggest an optimal fit. These results demon- strate the utility of the ARI across clinic and com- 0 munity-based samples in two countries and across HV (n = 76) FRBD (n = 35) BD (n = 39) SMD (n = 64) informants, suggesting that the scale can be used transnationally. The longitudinal stability of the ARI F (210, 3) = 96.34 F-test p<0.001 seems promising (at least by parent-report), al- ns HV vs. FRBD *** though this inference was drawn using a very small HV < BD *** Sheffe HV < SMD subsample and will require replication. *** FRBD < BD Post hoc *** FRBD < SMD Our second aim was to examine how the scale is ** BD < SMD associated with psychopathology. In the US sample, by parent-report, irritability was highest in SMD (B) compared with healthy volunteers, children at family Mean ARI score (95% CI) by diagnostic group risk for bipolar disorder, and BD. However, irritability self rated in BD was higher than in healthy volunteers or in 6 children at family risk for BD. By self-report, how- ever, differences in irritability between SMD and BD were non-significant, indicating that youth-report is less good at differentiating between these pheno- types. These results highlight the fact that a high level of chronic irritability, while a defining feature of SMD (Leibenluft et al., 2003), may also occur in children HV (n = 64) FRBD (n = 29) BD (n = 36) SMD (n = 65) with BD. It should also be noted that the BD pheno- type examined here is designed to be narrow, that is, F(190,3) = 20.85 F-test p<0.001 to only include children with elated or expansive ns HV vs FRBD *** mood, who may or may not also have irritability, but HV < BD *** Sheffe HV < SMD not the rare group of children (Hunt et al., 2009) ns FRBD < BD Post hoc *** presenting with episodic irritability only. FRBD < SMD ns BD < SMD In keeping with our hypothesis (Stringaris & Goodman, 2009a,b), parent-reported irritability was Figure 1 (A) Mean ARI score (95% CI) by diagnostic group par- the only predictor of emotional problems when com- ent-rated. ‘ns’ denotes no statistically significant differences, sample sizes reflect those with parent-report ARI data avail- pared with all other SDQ subscales in multivariate able.***p < 0.001, **p < 0.01. HV, healthy volunteers. FRBD, models; conversely, only hyperactivity, but not irri- children at family risk for bipolar disorder. BD, children with tability, predicted conduct problems. However, by bipolar disorder. SMD, severe mood dysregulation. (B) Mean ARI self-report, irritability and self-reported hyperactivity score (95% CI) by diagnostic group self-rated. ‘ns’ denotes no problems predicted emotional problems, and self-re- statistically significant differences, sample sizes reflect those with ported irritability also strongly predicted self-reported self-report ARI data available.***p < 0.001, **p < 0.01. HV, healthy volunteers. FRBD, children at family risk for bipolar dis- conduct problems. It should also be noted that in the order. BD, children with bipolar disorder. SMD, severe mood univariate analyses, irritability was related to either dysregulation emotional or conduct problems, by either reporting source. This suggests that irritability in this age group acts as an indicator of either conduct or emotional Discussion problems. As previously suggested (Stringaris, Zavos, This article reports on the characteristics of the ARI, Leibenluft, Maughan, & Eley, 2011), this relationship a concise parent- and self-reported questionnaire between irritability and conduct problems may itself designed to assess youth irritability. be mediated through headstrong and hurtful behav- Our first aim was to describe the basic character- iors, which were not controlled here. A related, but not istics of the scale in the US and UK samples. We identical, dimension of negative affect has been re- found a similar pattern of item frequencies across cently identified as part of oppositional problems reporting sources and samples, although the abso- (Burke, Hipwell, & Loeber, 2010). lute frequencies of the items varied. The two items on This study’s strengths include the use of samples prolonged anger were endorsed least often. More- across two countries spanning a number of diagnoses over, we found that while the item means between and ascertainment methods, and the comparison reporting sources were very similar in the UK between SMD and BD. However, it also has a number 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. doi:10.1111/j.1469-7610.2012.02561.x The Affective Reactivity Index 1115 Table 3 Pearson correlations (and 95% confidence intervals) between ARI and other SDQ scores. Parent-report is above and self- report below the diagonal (UK sample) Irritability Emotional Conduct Hyperactivity Peer Prosocial (ARI) (SDQ) (SDQ) (SDQ) (SDQ) (SDQ) Irritability (ARI) – 0.60 0.55 0.33 0.23 )0.55 (0.39 to 0.75) (0.31 to 0.72) (0.05 to 0.56) ()0.06 to 0.49) ()0.72 to )0.31) Emotional (SDQ) 0.66 – 0.36 0.48 0.28 )0.37 (0.52 to 0.77) (0.08 to 0.58) (0.23 to 0.67) ()0.00 to 0.53) ()0.59 to )0.09) ns Conduct (SDQ) 0.48 0.43 – 0.29 0.32 )0.21 (0.29 to 0.63) (0.24 to 0.59) (0.00 to 0.53) (0.04 to 0.55) ()0.46 to 0.08) ns ns Hyperactivity (SDQ) 0.39 0.38 0.49 – 0.04 )0.04 (0.19 to 0.56) (0.18 to 0.55) (0.30 to 0.64) ()0.24 to 0.32) ()0.32 to 0.25) ns Peer (SDQ) 0.30 0.38 0.28 0.25 – )0.06 (0.09 to 0.48) (0.18 to 0.55) (0.07 to 0.47) (0.03 to 0.44) ()0.22 to 0.34) ns Prosocial (SDQ) )0.57 )0.24 )0.21 )0.13 0.03 – ()0.67 to )0.36) ()0.43 to )0.02) ()0.41 to 0.00) ()0.33 to 0.09) ()0.24 to 0.19) ARI, Affective Reactivity Index; SDQ, Strengths and Difficulties Questionnaire. Parent-report n = 82 (one subject with ARI but no SDQ data); self-report: n = 48 (two subjects with ARI but no SDQ data). Table 4 Association between irritability, conduct, and emotion problems in the UK sample Outcomes Parent n = 81 Self n =48 Predictors Emotional (SDQ) Conduct (SDQ) Emotional (SDQ) Conduct (SDQ) Irritability (ARI) 0.61*** (0.38 to 0.84) 0.35 ()0.07 to 0.78) 0.36* (0.04 to 0.68) 0.63** (0.18 to 1.07) Hyperactivity (SDQ) 0.10 ()0.10 to 0.30) 0.50** (0.20 to 0.81) 0.36** (0.11 to 0.60) 0.18 ()0.20 to 0.55) Conduct (SDQ) 0.06 ()0.08 to 0.20) n/a )0.04 ().26 to 0.18) n/a Emotional (SDQ) n/a 0.15 ()022 to 0.52) n/a )0.08 ()052 to 0.37) Peer (SDQ) 0.15 ()0.03 to 0.33) 0.09 ()0.20 to 0.38) 0.21 ()0.03 to 0.45) 0.27 ()0.08 to 0.61) Prosocial (SDQ) 0.11 ()0.08 to 0.31) )0.02 ()0.34 to 0.30) )0.18 ()0.45 to 0.10) 0.04 ()0.36 to 0.45) ARI, Affective Reactivity Index; SDQ, Strengths and Difficulties Questionnaire. Beta coefficients (and confidence intervals) are reported from linear regression models; ***p < 0.001, **p < 0.01, *p < 0.05. Parent- reported outcomes were predicted by parent-reported variables and self-reported outcomes were predicted by self-reported variables. of weaknesses. First, the samples are subject to assess the importance of irritability to psychopa- referral and Berkson bias, limitations common to all thology. clinic-based studies (Caron & Rutter, 1991). To address this, the ARI should be validated in epidemi- Acknowledgements ologic samples. Second, the size of the UK sample is The authors have declared that they have no competing small. Future studies with larger numbers should be or potential conflicts of interest. This manuscript is conducted to examine how irritability predicts, for based on material funded by the Wellcome Trust. Argyris Stringaris gratefully acknowledges the support example, treatment outcomes in clinics. Third, the of the Wellcome Trust. cross-sectional nature of our main results limits the inferences that can be drawn. Fourth, this scale was not designed as an in-depth probe of the phenome- Correspondence to nology of irritability or of its relationship with pheno- Argyris Stringaris, King’s College London, Institute of types of more general emotional and behavioral Psychiatry, Denmark Hill, London, SE5 8AF, UK; dyscontrol (Holtmann et al., 2010). Further research Email: [email protected] is needed to understand these relationships. Also, the ARI was developed to capture irritability in a way that would be accessible to participants from as wide a Supporting information child age-range as possible. Future research should Additional supporting information is provided along determine whether it could also be used for adult self- with the online version of this article. report of irritability. Appendix S1: The Affective Reactivity Index. In conclusion, the ARI demonstrates promising Please note: Wiley-Blackwell are not responsible for psychometric properties and it may prove a useful the content or functionality of any supporting materials supplied by the authors. Any queries (other than tool for clinical and research purposes. Future missing material) should be directed to the corre- epidemiologic samples and clinic samples with sponding author for the article. treatment designs using the ARI may further 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health. 1116 Argyris Stringaris et al. J Child Psychol Psychiatry 2012; 53(11): 1109–17 Key points • Irritability is a form of mood dysregulation of intense scientific interest. • The Affective Reactivity Index is a concise (seven item) scale for the dimensional measurement of irritability. • The ARI has excellent internal consistency and forms a single factor in both parent- and self-report forms. • The parent- and self-reported ARI total score differentiates cases from controls in a clinic and a community sample. The parent-rated ARI total score also differentiates between youth with severe mood dysregulation and youth with bipolar disorder. • The ARI may be a useful tool for the measurement of irritability. Buss, A.H., & Durkee, A. (1957). An inventory for assesssing References different kinds of hostility. Journal of Consulting Psychology, Aebi, M., Asherson, P., Banaschewski, T., Buitelaar, J., 21, 343–349. 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Journal of the American Academy of Child and Published online: 10 May 2012 Adolescent Psychiatry, 49, 397–405. 2012 The Authors. Journal of Child Psychology and Psychiatry  2012 Association for Child and Adolescent Mental Health.

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