Fig. 2: Number of included studies and study participants per study design according to year of publication.

Number of included studies per year of publication and study design, including observational research assessing recreational cannabis users, experimental studies administering THC in healthy volunteers, and medicinal studies assessing adverse events in individuals taking cannabis products for medicinal use. Quasi-experimental research involved research testing the effects of THC administration in a naturalistic setting.23,62 k, number of studies; n, number of (non-overlapping) study participants.