© 2018 The British Pharmacological Society Cannabis is the most commonly used illicit substance worldwide and the prevalence of users continues to increase. Over the last 2 decades, the world has seen significant changes regarding cannabis for recreational use as well as application in its use as a therapeutic medicine. This is likely to have influenced the decreasing perception of risks associated with the use of cannabis. Cannabis, however, is not benign and, depending on the pattern of its use, can incur a range of harmful effects, which have implications when prescribing medicinal cannabinoids for individuals. Based on research evidence from recreational use of cannabis as well as the emerging data from trials of medicinal cannabis, we propose some clinical domains that will need specific considerations when prescribing medicinal cannabis.