CannaTrials adheres to evidence-based medicine – making statements based on medical evidence. This page is excerpted and quoted from the National Academies of Science, Engineering, and Medicine. A Committee of over 40 experts, researchers, and reviewers in The Health and Medicine Division published a 486 page report in 2017 entitled “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research.” If you would like to access the entire report you may do so by clicking this link.
Medical Marijuana and All-Cause Mortality
“The Institute of Medicine (IOM) report Marijuana and Medicine: Assessing the Science Base states that “epidemiological data indicate that in the general population marijuana use is not associated with increased mortality” (IOM, 1999, p. 109). More recently, modeling studies have estimated that a substantial disease burden—and the associated decrements in the quality and length of life—can be attributed to cannabis use (Degenhardt et al., 2013; Imtiaz et al., 2016). By contrast, a recent systematic review informed by epidemiological data did not report a statistically significant association between cannabis use and mortality (Calabria et al., 2010). This section reviews the available literature to assess the evidence and develop conclusions about cannabis-related mortality.
Sidney et al. (1997) found a statistically significant association between cannabis use and increased risk of all-cause mortality among men diagnosed with AIDS, but not among men without this diagnosis or among women. The authors suggest that the relationship between cannabis use and all-cause mortality among male AIDS patients was not causal; instead, it “most likely represented uncontrolled confounding by male homosexual behavior” (Sidney at al., 1997, p. 589). Limitations in Sidney et al. (1997) include the use of self-report without biological validation to assess patterns of cannabis use; the lack of post-baseline assessments of cannabis use, by which changes over time in the frequency of use could be documented; a lack of data on other substance use, creating the possibility for residual confounding; and, the inability to follow participants into later age, where potential long-term health effects of cannabis use may have emerged.
After accounting for potential confounders, Andreasson and Allebeck (1990) found no statistically significant association between cannabis use and mortality. Furthermore, although a high proportion of deaths among participants who reported smoking cannabis on 50 or more occasions by the time of conscription were due to suicide or uncertain suicide, use of narcotics was also common in these incidents, leading the authors to suggest that a “significant share of the mortality associated with cannabis abuse in this study is attributable to intravenous drug abuse” (Andreasson and Allebeck, 1990, p. 14). Limitations of the study include the use of nonanonymous self-report to collect data on patterns of cannabis use, and the lack of any post-baseline assessments of cannabis use.
Findings from Muhuri and Gfroerer (2011) are based on data from the 1991 National Health Interview Survey’s Drug and Alcohol Use supplemental questionnaire, and they indicate a lower prevalence of cannabis use than that seen in the 1991 National Household Survey on Drug Abuse (NHSDA) (45.2 percent versus 52.7 percent). If this discrepancy in the prevalence of cannabis use reported by two national surveys conducted in the same year is the result of underreporting by participants who died during the follow-up period, the mortality risk associated with cannabis use could have been underestimated. Other limitations include the use of self-report to collect data on patterns of cannabis use and the lack of post-baseline assessments to detect changes in cannabis use. Strengths of the study include a base population from a national household sample and an analysis that excluded users of other important illicit drug categories— heroin, cocaine, hallucinogens, and inhalants.
Findings from Manrique-Garcia et al. (2016) have several limitations. Risk estimates are based on cannabis use as of the time of conscription rather than lifetime cannabis exposure and therefore do not account for cannabis use during the ~40 year follow-up period. Similarly, data on potential confounders after the time of conscription is unavailable, so the extent to which they affected study participants and potentially impacted all-cause mortality risk is unknown. Finally, since data on cannabis use was collected by non-anonymous self-report without biological validation, cannabis use may have been underreported.
There is an overall dearth of cohort studies empirically assessing general population cannabis use and all-cause mortality. Although the available evidence suggests that cannabis use is not associated with an increased risk of all-cause mortality, the limited nature of that evidence makes it impossible to have confidence in these findings. These conclusions are not informed by the results of existing large-scale modeling studies that synthesized data from a variety of sources to estimate the burden of disease attributable to cannabis use (Degenhardt et al., 2013; Imtiaz et al., 2016). Although these studies were methodologically rigorous, their direct applicability to actual cannabis-related mortality rates in the United States is uncertain. Consequently, the committee chose not to include them in this review. Also excluded from review were studies of mortality among persons with known cannabis addiction or dependence, those who have been under medical treatment for these disorders, or those who were identified through a country’s criminal justice system, due to presence in these populations of important and often inadequately controlled confounders such as concurrent mental illness and poly-substance abuse.
CONCLUSION 9-1 There is insufficient evidence to support or refute a statistical association between self-reported cannabis use and all-cause mortality. “
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