Questions remain about the benefits and harms of cannabis

Despite dramatic changes in the legal landscape and usage rates of cannabis, evidence is still lacking regarding its potential health and therapeutic effects. Recently, the National Academies of Sciences, Engineering, and Medicine released its third comprehensive review of the literature surrounding cannabis and made recommendations for future research. The authors of an Ideas and Opinions piece published in Annals of Internal Medicine summarized the group's key findings in an effort to educate physicians on the most relevant health outcomes of cannabis use and the potential therapeutic indications for cannabis and cannabinoid products.

Currently, 28 states and the District of Columbia legalized cannabis for medical use and 7 states and the District of Columbia also allow recreational cannabis use. In those states that allow some access to cannabis compounds, cancer, HIV/AIDS, multiple sclerosis, glaucoma, seizures and epilepsy, and pain are among the most recognized qualifying conditions for cannabis therapy. The committee found substantial evidence that cannabinoid products were modestly effective in the short term for reducing chronic pain. However, many studies used purified oral cannabinoid preparations and most trials were short term and conducted in patients with neuropathic pain, which limits the generalizability of the findings.

The group also examined the evidence about the harms of cannabis use. Substantial evidence supports a link between long-term cannabis smoking and adverse respiratory symptoms. Smoking cannabis was also shown to be associated with several other negative effects, including the development of schizophrenia and other psychoses among the most frequent users.