CANNABIS USE DISORDER AND PSYCHOSIS: A DEVELOPING PROBLEM
Mounting epidemiological evidence indicates that the development of cannabis use disorder (CUD) may potentiate psychosis risk. Recent large-scale studies have shown a four-fold increase over the last two decades in the proportion of schizophrenia that can be attributable to CUD in Denmark (cited in [1, 2]) and a near tripling of CUD-associated psychosis cases in Ontario [2]. The largest-to-date genetic study also indicated that CUD was most associated with schizophrenia compared to other psychiatric disorders [3]. Psychosis most often develops during late teens and early adulthood, while cannabis use is often initiated at a younger age [4]. In Ontario, the prevalence of CUD among adolescents has risen substantially, and CUD-associated psychosis cases are most evident from ages 19–24 [2]. Alongside rising rates of CUD, cannabis potency has increased dramatically, which has raised concerns for impacts on these psychiatric outcomes [5]. A multi- site study indicated that daily users of potent products are 5x more likely to develop a psychotic disorder [4], and use of these products increases the likelihood of developing CUD/problematic use [5]. Neurobiological substrates that develop during adolescence and are vulnerable to cannabis likely contribute to the emergence of CUD, psychosis, or both.