MARIJUANA USERS MAY BE MORE PRONE TO PSYCHOSIS: STUDY

Those Who've Smoked For At Least 6 Years Are Twice As Likely To Have
Delusions As Non-Users

Young people who smoke cannabis or marijuana for six years or more are
twice as likely to have psychotic episodes, hallucinations or
delusions than people who have never used the drug, scientists said
Monday.

The finding adds weight to previous research that linked psychosis
with the drug -- particularly in its most potent form as "skunk" --
and will feed the debate about the level of controls over its use.

Despite laws against it, up to 190 million people around the world use
cannabis, according to United Nations estimates, equating to about
four per cent of the adult population.

John McGrath of the Queensland Brain Institute in Australia studied
more than 3,801 men and women born between 1981 and 1984 and followed
them up after 21 years to ask about their cannabis use and assessed
them for psychotic episodes. Around 18 per cent reported using
cannabis for three or fewer years, 16 per cent for four to five years
and 14 per cent for six or more years.

"Compared with those who had never used cannabis, young adults who had
six or more years since first use of cannabis were twice as likely to
develop a non-affective psychosis (such as schizophrenia)," McGrath
wrote in a study published in the Archives of General Psychiatry journal.

They were also four times as likely to have high scores in clinical
tests of delusion, he wrote, and a so-called "dose-response"
relationship showed that the longer the duration since first cannabis
use, the higher the risk of psychosis-related symptoms.

A study by British scientists last year suggested that people who
smoke skunk, a potent form of cannabis, are almost seven times more
likely to develop psychotic illnesses such as schizophrenia than those
who smoke "hash" or cannabis resin.

Previous studies had also suggested smoking cannabis can double the
risk of psychosis, but the British study was the first to look
specifically at skunk. Skunk has higher amounts of the psychoactive
ingredient THC, which can produce psychotic symptoms such as
hallucinations, delusions and paranoia.

McGrath said, however, that "The nature of the relationship between
psychosis and cannabis use is by no means simple" and that more
research was needed to examine the mechanisms at work.

As part of his study, McGrath and his team looked at links between
cannabis use and psychotic symptoms among a group of 228 sibling pairs
and found the association still held. This suggests other influences
such as genes or the environment were less likely to be responsible
for the psychosis, they said.

An international group of drug policy experts published a book earlier
this year arguing that laws against cannabis have failed to cut its
use but instead led to vast numbers of arrests for drug possession in
countries such as Britain, Switzerland and the United States, which
causes social division and pointless government expense.