10 May 2007
Cannabis use is strongly associated
with the development of psychosis among people at risk of the
disorder, research indicates.
The finding supports the notion that cannabis use is a risk factor
for schizophrenia and strengthens the case for screening and
monitoring at-risk individuals for cannabis use.
Study authors Karin Kristensen and Kristen Cadenhead (University
of California at San Diego, La Jolla, USA) tested the link between
cannabis use and psychosis among participants in the Cognitive
Assessment and Risk Evaluation (CARE) Program.
CARE is a longitudinal program for individuals deemed to be at
risk for developing a psychotic disorder, based on the presence of
subsyndromal psychotic symptoms, a family history of
schizophrenia, and/or a recent deterioration in global
During 1 year of follow-up, six (12.5%) of the 48 patients made
the transition to psychosis. The transition rate was 3.1% among
participants reporting no or minimal cannabis use versus 31.3%
among those who met criteria for cannabis abuse or dependence.
The difference between cannabis users and non-users was
statistically significant, Kristensen and Cadenhead report in the
journal Psychiatry Research.
Further analyses found no association between alcohol or cocaine
use and the conversion to psychosis; in contrast, nicotine use was
significantly tied to later development of psychosis.
The authors admit that their findings are limited by the small
sample size and reliance on self-reported measures of cannabis
use. They call for future studies to address these limitations.
"Psychoeducation regarding the deleterious effects of cannabis use
in vulnerable individuals could discourage use, and perhaps
improve outcome," they conclude.
Psychiatry Research 2007;