Cannabis use has been described as one of many environmental influences associated with an individual’s increased vulnerability towards the development of psychotic illness [13, 35, 38, 61], with approximately one in every four individuals in this population presenting with a concurrent CUD diagnosis [89]. Several studies have demonstrated negative effects of cannabis use in patients with schizophrenia. Specifically, THC in cannabis has been associated with an increased risk of psychosis in a dose-dependent manner: regular cannabis users and heavy cannabis users are 2- and 4-times more likely to develop psychosis, respectively [39, 100]. Furthermore, increased risk for earlier psychotic symptom presentation has been observed in conjunction with cannabis use in the general population [70, 81]. Results from one of the largest longitudinal studies involving over 50,000 male participants indicates that those who smoked cannabis by the age of 18 had twice the risk for receiving a diagnosis of schizophrenia, while those who used chronically were at six times the risk compared to non-users [2]. Notably, the administration of intravenous THC in healthy individuals has been shown to directly induce psychotic
