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Long-term Marijuana Use and Pulmonary Function

Long-term Marijuana Use and Pulmonary Function To the Editor: Dr Pletcher and colleagues1 studied the association between marijuana and pulmonary function over 20 years. Although all survey analyses can be limited by recall bias,2 the risk of bias in this study may be greater than usual. Cognitive deficits may exist in chronic marijuana users that are dose-dependent, with higher doses leading to poorer recall.3,4 Such decline in long-term memory may result in inaccurate recollection of smoking frequency, particularly during the 10-year intervals between interviews in the Coronary Artery Risk Development in Young Adults (CARDIA) study population. Data also have shown that users who inhale marijuana with a vaporizer have fewer respiratory symptoms, even when adjusted for the amount used.5 Because the delivery vehicle may play an important role in assessing marijuana's association with pulmonary function, a subgroup analysis on the mode of inhalation would strengthen this study's findings. We were unable to locate in the article the methods describing the selection and retention of the study cohort (extracted from the original CARDIA group) or the selection of certain subgroups. A 69% retention rate was reported at 20 years; however, only 2807 of the original 5016 participants (56%) were documented in Table 1 of the article, without an explanation for the apparent loss to follow-up. The percentage of individuals with income greater than $50 000 per year listed in Table 1 also appears to reflect an undefined subgroup of respondents rather than the original cohort. This topic has been sparsely studied, although it may arise frequently in patient-physician discussions given the increasing legal and clinical arguments around marijuana use. However, because of the inherent limitations in this study's design, we believe marijuana's association with lung function remains ambiguous. Back to top Article Information Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. References 1. Pletcher MJ, Vittinghoff E, Kalhan R, et al. Association between marijuana exposure and pulmonary function over 20 years. JAMA. 2012;307(2):173-18122235088PubMedGoogle ScholarCrossref 2. Grimes DA, Schulz KF. Bias and causal associations in observational research. Lancet. 2002;359(9302):248-25211812579PubMedGoogle ScholarCrossref 3. Indlekofer F, Piechatzek M, Daamen M, et al. Reduced memory and attention performance in a population-based sample of young adults with a moderate lifetime use of cannabis, ecstasy and alcohol. J Psychopharmacol. 2009;23(5):495-50918635709PubMedGoogle ScholarCrossref 4. Johnson RA, Gerstein DR, Rasinski KA. Adjusting survey estimates for response bias: an application to trends in alcohol and marijuana use. Public Opin Q. 1998;62(3):354-377Google ScholarCrossref 5. Earleywine M, Barnwell SS. Decreased respiratory symptoms in cannabis users who vaporize. Harm Reduct J. 2007;4:1117437626PubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Long-term Marijuana Use and Pulmonary Function

JAMA , Volume 307 (17) – May 2, 2012

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Publisher
American Medical Association
Copyright
Copyright © 2012 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.2012.3570
Publisher site
See Article on Publisher Site

Abstract

To the Editor: Dr Pletcher and colleagues1 studied the association between marijuana and pulmonary function over 20 years. Although all survey analyses can be limited by recall bias,2 the risk of bias in this study may be greater than usual. Cognitive deficits may exist in chronic marijuana users that are dose-dependent, with higher doses leading to poorer recall.3,4 Such decline in long-term memory may result in inaccurate recollection of smoking frequency, particularly during the 10-year intervals between interviews in the Coronary Artery Risk Development in Young Adults (CARDIA) study population. Data also have shown that users who inhale marijuana with a vaporizer have fewer respiratory symptoms, even when adjusted for the amount used.5 Because the delivery vehicle may play an important role in assessing marijuana's association with pulmonary function, a subgroup analysis on the mode of inhalation would strengthen this study's findings. We were unable to locate in the article the methods describing the selection and retention of the study cohort (extracted from the original CARDIA group) or the selection of certain subgroups. A 69% retention rate was reported at 20 years; however, only 2807 of the original 5016 participants (56%) were documented in Table 1 of the article, without an explanation for the apparent loss to follow-up. The percentage of individuals with income greater than $50 000 per year listed in Table 1 also appears to reflect an undefined subgroup of respondents rather than the original cohort. This topic has been sparsely studied, although it may arise frequently in patient-physician discussions given the increasing legal and clinical arguments around marijuana use. However, because of the inherent limitations in this study's design, we believe marijuana's association with lung function remains ambiguous. Back to top Article Information Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. References 1. Pletcher MJ, Vittinghoff E, Kalhan R, et al. Association between marijuana exposure and pulmonary function over 20 years. JAMA. 2012;307(2):173-18122235088PubMedGoogle ScholarCrossref 2. Grimes DA, Schulz KF. Bias and causal associations in observational research. Lancet. 2002;359(9302):248-25211812579PubMedGoogle ScholarCrossref 3. Indlekofer F, Piechatzek M, Daamen M, et al. Reduced memory and attention performance in a population-based sample of young adults with a moderate lifetime use of cannabis, ecstasy and alcohol. J Psychopharmacol. 2009;23(5):495-50918635709PubMedGoogle ScholarCrossref 4. Johnson RA, Gerstein DR, Rasinski KA. Adjusting survey estimates for response bias: an application to trends in alcohol and marijuana use. Public Opin Q. 1998;62(3):354-377Google ScholarCrossref 5. Earleywine M, Barnwell SS. Decreased respiratory symptoms in cannabis users who vaporize. Harm Reduct J. 2007;4:1117437626PubMedGoogle ScholarCrossref

Journal

JAMAAmerican Medical Association

Published: May 2, 2012

References