Cannabis use is associated with the onset of psychotic symptoms, but whether the link is causal remains controversial. This systematic review of 1653 studies identified six risk factors that increase the likelihood of psychosis among cannabis users, ranked by importance: dose-response relationship (quantity, frequency, and duration of use), early age of first use, genetic susceptibility, childhood trauma, cigarette smoking, and urban environment. In contrast, cannabidiol (CBD) is associated with fewer psychotic symptoms and appears to have antipsychotic properties. The authors conclude that further research is needed to establish a clear causal relationship and to determine how much each risk factor contributes to the onset and persistence of psychosis.
Cannabis consumption appears to increase the risk of psychotic symptoms, but whether it causes psychosis remains uncertain. A review of ten epidemiological studies found that three supported a causal link between cannabis use and diagnosed psychosis, five suggested chronic use increases psychotic symptoms without leading to diagnosed psychosis, and two found no causal relationship. Heavy consumption, prolonged use, early exposure, and underlying psychotic vulnerability may contribute. Potential neurobiological mechanisms involve dopamine, endocannabinoids, and brain growth factors. Uncertainty persists due to challenges in measuring cannabis use and psychosis, possible reverse causality, and residual confounding factors.