(March 1, 2010 - Insidermedicine)

Using cannabis in adolescence, particularly early in adolescence, is associated with an increased risk of developing psychotic symptoms, according to research published online ahead of print in the Archives of General Psychiatry.

Here is some information on psychosis:

•       It is a mental disorder primarily characterized by the presence of hallucinations and/or delusions

•       Hallucinations are the experience of perceiving things, such as voices, that are not present in the external world

•       Delusions are beliefs, often strange or bizarre, that are not objectively true

Researchers from the University of Queensland followed nearly 4,000 young adults who were born between 1981 and 1984. During a follow-up period that took place when the participants were an average of 20.1 years of age, they were asked about previous cannabis use and tested for the presence of psychosis.

Overall, 65 of the study participants were diagnosed with psychosis, and 223 had signs of having experienced hallucinations. In addition, about 18% reported using cannabis for three or fewer years, 16% for four to five years, and 14% for six or more years. The longer the period since first using cannabis, the greater the risk of having psychotic symptoms. For instance, 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  psychosis and four times as likely to have a high score on a test that indicates the presence of delusions as someone who had never used cannabis.

Today's research highlights the complex relationship between psychosis and cannabis use – it is possible that individuals experiencing early symptoms of psychosis are more likely to try cannabis and that long-term use of this drug increases the risk for psychosis in vulnerable individuals.