SMOKING POT WON'T MAKE YOU CRAZY, BUT DECIPHERING POT PROPAGANDA MIGHT

Smoking pot won't make you crazy, but trying to find the truth
behind the recent rash of headlines regarding a supposed link
between cannabis and mental illness might.

According to the Associated Press and other news sources, a new
study in the British medical journal The Lancet reports that smoking
cannabis -- even occasionally -- can increase one's risk of becoming
psychotic. It sounds alarming at first, but a closer look at the
evidence reveals that there's less here than the headlines imply.

First, there is no new study. The paper published in The Lancet is a
meta-analysis -- a summary of seven studies that previously appeared
in other journals, including some that were published decades ago.
Second, the touted association between cannabis and mental illness
is small -- about the same size as the link between head injury and
psychosis. Finally, despite what some new sources suggest, this
association is hardly proof of a cause-and-effect relationship
between cannabis and psychosis,

So why the sudden fuss?

Part of the answer is political. New British Prime Minister Gordon
Brown longs to stiffen penalties against marijuana users. One way to
justify this move involves convincing the public that The Lancet
proved that puffing the weed will make you batty. Of course, that's
not what the article says at all.

In fact, investigators actually reported that cannabis use was
associated with a slight increase in psychotic outcomes. However,
the authors emphasized (even if many in the media did not) that this
small association does not reflect a causal relationship. Folks with
psychoses use all intoxicants more often than other people do,
including alcohol and tobacco.

Cannabis use can correlate with mental illness for many reasons.
People often turn to cannabis to alleviate the symptoms of distress.
A recent study performed in Germany showed that cannabis offsets
certain cognitive declines in schizophrenic patients. Another study
shows that psychotic symptoms predict later use of cannabis,
suggesting that people might turn to the plant for help rather than
become ill after use.

Perhaps the most impressive evidence against the cause-and-effect
relationship concerns the unvarying rate of psychoses across
different eras and different countries. People are no more likely to
be psychotic in Canada or the United States (two nations where large
percentages of citizens use cannabis) than they are in Sweden or
Japan (where self-reported marijuana use is extremely low). Even
after the enormous popularity of cannabis in the 1960s and 1970s,
rates of psychotic disorders haven't increased.

Despite this evidence, we'd like to spread the word that cannabis is
not for everybody. Teens should avoid the plant. Folks with a
predisposition for mental illness should stay away, too. This
potential for health risks in a few people, however, does not
justify criminal prohibitions for everyone. (We wouldn't
pass blanket prohibitions against alcohol simply to
protect pregnant women, for example.) The underground market does
an extremely poor job of keeping marijuana out of the hands of teens
and others who should stay away from it. A regulated market could
better educate users to potential risks and prohibit sales to young people.

Consequently, the review in The Lancet suggests that if cannabis
really does alter risk for mental illness, we can't leave control of
sales to folks who are willing to break the law. Instead, a taxed,
regulated, age-restricted market is our best chance to keep any
negative consequences of marijuana under control.