A single dose of tetrahydrocannabinol (THC), the psychoactive component in cannabis, may induce psychotic, depressive and anxiety symptoms in healthy adults, according to a systematic review.

UK researchers examined 15 studies, including 331 people with no history of psychotic or other major psychiatric disorders.

The studies investigated participants’ psychiatric symptoms following acute administration of IV, oral or nasal THC, cannabidiol (CBD) and placebo, as measured by the Brief Psychiatric Rating Scale and the Positive and Negative Syndrome Scale.

Scores for an increase in severity of positive psychotic symptoms (including delusions and hallucinations), negative psychotic symptoms (such as blunted affect and amotivation) and general symptoms (including depression and anxiety) were compared.