(March 1, 2010 - Insidermedicine)

Cannabis use in adolescence, particularly if it started early in adolescence, is associated with an increased risk for developing psychosis, according to research published online ahead of print in the Archives of General Psychiatry.

Here are some recommendations for the treatment of marijuana use disorders, from the American Psychiatric Association:

•       Studies of treatment for marijuana use disorders are limited.

•       No specific pharmacotherapies for marijuana withdrawal or dependence can be recommended

•       An intensive relapse prevention approach that combines motivational interventions with the development of coping skills may be effective for the treatment of marijuana dependence

Researchers out of the University of Queensland followed 3,801 young adults born between 1981 and 1984. At a 21-year follow-up, when the participants' mean age was 20.1 years, they were asked about cannabis use in recent years and assessed for psychosis.

Overall, 65 study participants were diagnosed with non-affective psychosis, and 223 had at least one positive item for hallucination on a diagnostic interview. In addition, 17.7% reported using cannabis for three or fewer years, 16.2% for four to five years, and 14.3% for six or more years. The longer the period since the first use of cannabis, the greater the risk of multiple psychosis-related outcomes. For example, a participant who had first used cannabis six or more years previously, at age 15 or younger, was twice as likely to receive a diagnosis of non-affective psychosis and four times as likely to have a high score on the Peters et al Delusions Inventory as someone who had never used cannabis. The association persisted even in sibling pairs.

Today's research highlights the complex relationship between cannabis use and psychosis.