Effect of Cannabis on Mortality
"In summary, this study showed little, if any, effect of marijuana use on non-AIDS mortality in men and on total mortality in women. The increased risk of AIDS mortality in male marijuana users probably did not reflect a causal relationship, but most likely represented uncontrolled confounding by male homosexual behavior. The risk of mortality associated with marijuana use was lower than that associated with tobacco cigarette smoking."
Stephen Sidney, MD, Jerome E. Beck, DrPH, Irene S. Tekawa, MA, Charles P Quesenberry, Jr, PhD, and Gary D. Friedman, MD, “Marijuana Use and Mortality.” American Journal of Public Health 87.4 (1997) pp. 589–590.