Are Smoking Pot and Psychosis Linked?
Marijuana Boosts Later Psychotic Illness Risk by 40%, Study Shows
Lancet Editors Change Tune
In an accompanying comment, two scientists from Copenhagen University
Hospital echo Zammit's belief that "there is a need to warn the public of
these dangers, as well as to establish treatment to help young, frequent
In an editorial in the same issue, Lancet editors note that the
publication ran an oft-quoted editorial in a 1995 issue stating that "the
smoking of cannabis, even long term, is not harmful to health." Now, the
editors note, research published in the interim, including the meta-analysis,
has triggered a change in their thinking, with them now stating that cannabis
use "could increase the risk of psychotic illness" and that more
research is needed on any link with depression and anxiety.
NORML Begs to Differ
If the association exists between marijuana use and psychotic illness,
"we would have seen the negative effects they were warning about if they
were significant," says Paul Armentano, a senior policy analyst for the
National Organization for the Reform of Marijuana Laws (NORML), based in
Most Western cultures, he tells WebMD, have witnessed "an explosion
among marijuana use among adults and young people.
"Where is the explosion in cannabis-related mental illness?" he
asks. "The paper says, 'You are right, we haven't seen it. Maybe it is a
Armentano argues the rise in mental illness would have already occurred if
the link exists.
Armentano also wonders if the psychosis may have come first, before the
marijuana use, for some people. In the paper, the authors note that such
reverse causation is not likely for psychosis but that the studies of marijuana
and depression did not adequately address the possibility of reverse
Politics in the U.K. may be driving the effort to analyze an association
between marijuana and mental illness, Armentano tells WebMD. Prime Minister
Gordon Brown has been quoted in the British press as saying he has never used
cannabis, even as cabinet ministers tell about their cannabis-filled younger
days. In 2004, the U.K. downgraded cannabis to a class C drug, reducing
penalties for possession, production, and supply.
Now, the Advisory Council on the Misuse of Drugs in the U.K. will look at
evidence for harms caused by cannabis and discuss whether the drug should be
relabeled, perhaps as a class B drug of misuse, with stiffer penalties for