Purpose: Cannabis is the most widely used illicit substance and one of the most commonly used psychoactive substances in the world, preceded only by alcohol, tobacco and caffeine. Recent changes in legislation regarding cannabis use in Canada and potential upcoming changes worldwide may have a further impact on the prevalence of cannabis use. Thus, it is critical to understand the risks and potential adverse health effects of acute and long-term cannabis use. Current literature is lacking in many areas surrounding cannabis use, and for the most part is unable to provide clear associations once confounding variables are considered. Here we provide a general overview of the history of cannabis, the physical and mental health consequences, and the risks to specific groups. Source: A scoping search of published articles in PubMed from the start date (1946) until 2018. Principal finding: Current evidence supports an association between cannabis use and mild respiratory and cardiac effects, but no clear increased risk of cancer. Psychiatric disorders, including schizophrenia and anxiety, show associations with cannabis use; however, a causal effect of cannabis use is unclear. While no evidence for increased risk in pregnancy has been found, risk is still undetermined. Youth may be at a greater risk as earlier initiation of use increases the risk of adverse health effects. Conclusion: Overall, evidence for direct and long-term adverse effects of cannabis use is minimal and additional longitudinal studies will be required to better delineate unidentified effects.