Cannabis and neuropsychiatry, 1: benefits and risks.

Cannabis is popularly believed to be a relatively benign substance. Cannabis is also considered to have potential medical benefits, and medical marijuana has been legislated in many parts of the world. However, a recent meta-analysis found that cannabinoids were associated with only modest benefits for chemotherapy-related nausea and vomiting, small and inconsistent benefits for pain and spasticity, and inconclusive benefits for other indications such as improvement of appetite and weight, reduction in tic severity, and improvement of mood or sleep. On the flip side, cannabinoids and cannabis have acute and long-term adverse effects. In randomized controlled trials, cannabinoids increase the risk of total adverse events, serious adverse events, and dropout due to adverse events. Cannabis impairs cognition, and driving after cannabis use is associated with an increased risk of traffic accidents, including fatal accidents. Long-term cannabis use may lead to dependence, respiratory conditions, psychosis, and possibly cancer, as well. Cannabis use during pregnancy may compromise certain pregnancy outcomes such as fetal growth, and use during adolescence may compromise neurodevelopment, social adjustment, and vocational success. The composition and bioavailability of cannabis vary across preparations of the substance and routes of administration; this limits the ability to generalize the findings of studies. The findings of older research may no longer apply to current strains of cannabis that are higher in psychotogenic content. It is important for medical professionals and the lay public to understand the limitations of the efficacy data and the seriousness of the risks associated with cannabis use in medical and recreational contexts.