Proportion of patients in south London with first-episode psychosis attributable to use of high potency cannabis: a case–control study.

The authors obtained data from 410 patients with first-episode psychosis and 370 population controls in south London between May 1,2005 and May 31, 2011. The risk of individuals having a psychotic disorder showed a roughly three-times increase in users of “skunk-like” cannabis (high potency THC with minimal or no CBD) compared with those who never used cannabis. The risk of developing a psychotic disorder increased with increased frequency of use.

By Forti M., Marconi A., Carra E., Fraietta S., Trotta A., Bonomo M. et al

Read the full study at APA PsychNet.