• Marijuana Smoking and the Risk of Developing COPD, Lung Cancer, And/or Chronic Respiratory Symptoms: A Systematic Review

      Byers, Chris; The University of Arizona College of Medicine - Phoenix; Campos-Outcalt, Douglas (The University of Arizona., 2017-06-01)
      The aim of this study is to conduct a systematic review of the existing evidence on marijuana use and its association, or the absence of an association, with an increased risk of developing chronic obstructive pulmonary disease (COPD), lung cancer, and/or chronic respiratory symptoms. We hypothesize that a systematic review will not demonstrate sufficient evidence to determine that marijuana use increases the risk of developing COPD, lung cancer, and/or chronic respiratory symptoms. The term “chronic respiratory symptoms” encompasses the following: cough, sputum production, wheeze, shortness of breath, acute bronchitis, and chest tightness. The following databases were searched for the topics of marijuana smoking, COPD, lung cancer, and chronic respiratory symptoms: MEDLINE (PubMed/OvidSP), the Cochrane Controlled Trials Register, the Cochrane Database of Systematic Reviews, PsycINFO, the Database of Abstracts of Reviews of Effects, and Google Scholar. The search ended September 7th, 2016. Studies were initially limited only by the requirement that they were based upon human research and published in English. Studies were included if they were systematic reviews, randomized controlled trials (RCTs), prospective or retrospective cohort studies, case control studies, or cross‐sectional studies. A total of 739 articles were screened for eligibility, 17 unique studies met the inclusion criteria and underwent qualitative analysis1‐17. The quality of systematic reviews was evaluated using the AMSTAR criteria18; cohort, case‐control, and cross sectional studies were evaluated based upon the Newcastle‐Ottawa Quality Assessment Scale (NOS) 19. No RCTs were identified. The overall quality of the evidence for each outcome was determined by utilizing the GRADE methodology20‐21. Studies were primarily assessed by a single reviewer, with random validation of assessments on a limited number of studies by a second reviewer. Overall, there is very low quality evidence that assesses for an association between marijuana smoking and an increased risk of developing lung cancer, COPD, and/or chronic respiratory symptoms. There was no conclusive finding for lung cancer and COPD. However, seven of eight studies concluded that there was an association between marijuana use and chronic respiratory symptoms. The totality of evidence describing any associations between marijuana smoking and the risk of developing lung cancer, COPD, and/or chronic respiratory symptoms is not strong enough to confidently state that marijuana use is associated with any of these chronic pulmonary conditions. Of all the evidence examined in this systematic review, the most convincing appears to be that relating to a potential positive association between marijuana smoking and the risk of developing chronic respiratory symptoms. Unfortunately, the overall quality of evidence was very low due to significant methodological weaknesses within the studies. Thus, there is insufficient evidence in the current literature to make a definitive statement regarding this possible association.
    • Marijuana Use and the Risk of Depression: A Systematic Review and Meta‐Analysis

      Gentry, James; The University of Arizona College of Medicine - Phoenix; Campos-Outcalt, Douglas (The University of Arizona., 2016-03-25)
      Objective: To conduct a systematic review of the evidence pertinent to the relationship between marijuana use and depression and perform a meta‐analysis on the data in order to inform evidenced‐based practice. The question of interest is: Is marijuana use associated with increased risk of developing depression? Methods: The databases MEDLINE (PubMed), The Cochrane Library, CINAHL (EBSCO), psycINFO, and Google Scholar were searched for the topics of marijuana use and depression through October of 2013. Studies were included if they were systematic reviews, randomized controlled trials, prospective or retrospective cohort studies, or case‐control studies. No randomized controlled trials were discovered. Quality of cohort and case‐control studies was evaluated using the Newcastle‐Ottawa Quality Assessment Scale 1. Overall quality of evidence was determined using the GRADE methodology 2,3. The Bradford‐Hill criteria 4 were used to assess for causation. Studies were assessed by two reviewers. 173 articles were screened for eligibility. Of these fourteen articles were considered to fit the inclusion criteria. Nine homogeneous studies were included in the meta‐analysis. Results: The quality of the evidence reviewed is low to very low. It does not meet Bradford‐Hill criteria for causation. There is a slight positive correlation between marijuana use and onset of depression. However, those studies included in the meta‐analysis demonstrated a low overall pooled odds ratio (OR = 1.17; 95% CI = 1.06—1.29). Conclusion: The evidence suggests a slight positive correlation between marijuana use and depression but is not sufficient to draw a conclusion. This evidence is generally of very low quality. It does not demonstrate a dose response, and is without a significant magnitude of effect.