March 2, 2010 -- Young adults who are longtime pot smokers are more likely to have hallucinations, delusions, or to display signs of psychosis than short-term smokers or people who've never smoked marijuana.

The finding comes from a study of 3,801 young adults who were asked about their pot use and then evaluated to determine if they'd experienced "psychotic outcomes."

The study appears online in advance of print in the May issue of the Archives of General Psychiatry.

Youths who had experienced hallucinations early in life were more likely to have used marijuana longer, and more frequently, the study shows.

The study also suggests that more research is needed to determine whether people who are predisposed to psychosis might be more likely to smoke marijuana earlier in life and for longer periods.