(Marijuana Use and Cognition) "Other studies have found short term residual effects of cannabis use on memory and cognition (34, 35) that are more severe among women (36) and heavy users (37). However, our data suggest that over the long term cannabis use is not associated with greater declines in cognition among men, women, or heavy users. The study design we used included several of the features proposed by Pope et al.
"Several meta-analyses of multiple studies found that the risk of being involved in a crash significantly increased after marijuana use13 -- in a few cases, the risk doubled or more than doubled.14-16 However, a large case-control study conducted by the National Highway Traffic Safety Administration found no significant increased crash risk attributable to cannabis after controlling for drivers’ age, gender, race, and presence of alcohol.17"
Eight states have legalized adult (aged 21 and older) personal use of marijuana and legally regulate the production, distribution, and sale of marijuana: Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon, and Washington state. Additionally, the state of Vermont and the District of Columbia have legalized limited personal possession and cultivation of marijuana by adults aged 21 and older.
Effect of Cannabis Use by Adolescents on Cognition and IQ and the Potential Influence of Tobacco: "Compared with those in our sample who had never tried cannabis, teenagers who had used cannabis at least 50 times were 17 times more likely (84% vs. 5%) to have smoked cigarettes more than 20 times in their lifetime. Accounting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both IQ and educational performance.
Effect of Marijuana Use by Adolescents on Cognition and IQ: "In summary, the notion that cannabis use itself is causally related to lower IQ and poorer educational performance was not supported in this large teenage sample. However, this study indeed has limitations, in particular the young age of outcome assessment.
Effect of Marijuana Use by Adolescents on Cognition and IQ Development
Cannabis and 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."