New Study Indicates Cannabis-Associated Psychosis Risk Is Minimal
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May 1, 2008 - Albany, NY, USA
There is little increased risk of incidences of psychosis or
schizophrenia stemming from the use of cannabis, according to clinical
data to be published in the journal Human Psychopharmacology.
study found that participants who used cannabis, but no other illicit
substances did not score higher on a Schizotypal Personality
Questionnaire (SPQ) compared to those respondents who used legal drugs
only. However, those participants who used cannabis and other illicit
drugs such as ecstasy and cocaine did score higher on the SQP tests.
The study’s results contradict widely reported news reports alleging that marijuana use is associated with a much higher risk of psychosis.
previous work on the link between marijuana use and psychotic symptoms
has not controlled for other drug use at all," said NORML Advisory
Board member Mitch Earleywine,
who co-authored the study. "Other studies only use rough measures of
lifetime use of a few drugs. We focused on nine different drugs and
emphasized the stimulants, which work in a neurotransmitter system
linked closely to psychosis."
A prior review of cannabis and psychosis conducted by Britain’s Advisory Council on the Misuse of Drugs (ACMD) stated in a 2006 release
that, "the current evidence suggests, at worst, that using cannabis
increases lifetime risk of developing schizophrenia by one percent."
concurs with that assessment. "In my opinion, if cannabis has any
impact on psychosis at all it would only appear in folks who have a
genetic predisposition who also use heavily early in life," he said.
NORML published a white paper
last May which called for the regulation of cannabis as a means to
discourage its use by patients who may be predisposed to certain mental
Advocates for tougher marijuana laws in Britain have been trumpeting
the pot-and-psychosis link as a major impetus for Prime Minister Gordon
Brown’s expected move to elevate cannabis from a Class C to a Class B
drug. The ACMD declined
to back the move in a recent meeting on April 4, with 20 out of the
panel’s 23 experts deciding there was not sufficient new scientific
evidence to justify a change.
For more information, please contact NORML Deputy Director Paul Armentano at firstname.lastname@example.org. Full text of the study, "Polydrug Use, Cannabis Use, and Psychosis-Like Symptoms," will appear in Human Psychopharmacology.
updated: May 01, 2008