MARIJUANA'S RISKS BECOME BLURRIER

The federal government's war on drugs gets plenty of ammunition from
scientific studies that have correlated the use of such substances to
various psychological problems. Conspicuously absent, however, are
data showing that marijuana, one of the most widely used illicit
drugs, causes mental or behavior problems in teenagers and young
adults, a new report concludes.

The causal chain of events could just as easily run in the opposite
direction, suggests psychologist John Macleod of the University of
Birmingham in England and his colleagues in the May 15 Lancet.
Available evidence is consistent with the possibility that various
psychological and social difficulties foster mairjuana use, which may
then contribute to a worsening of those problems, Macleod's group contends.

After reviewing 48 relevant multiyear studies published between 1975
and 2003, the team focused on 16 investigations that had regularly
assessed large samples of children or teenagers for at least 10 years.

"We've found no strong evidence that use of [marijuana] in itself has
important consequences for psychological or social health, but we
cannot exclude the possiblity that such a relation exists," Macleod
says.

He and his colleagues are particularly skeptical of recent reports
from Sweden and New Zealand that around 1 in 10 teenagers who had
smoked marijuana experienced schizophrenia symptoms by young
adulthood. It's doubtful that marijuana plays a direct role in
schizophrenia, Macleod's group argues, because the mental disorder's
worldwide incidence has remained stable while the proportion ot teens
reporting marijuana use has fluctuated.

Psychiatrist Herbert D. Kleber of Columbia University says that this
argument underplays the increased risk of schizlphrenia reported in
the Swedish and New Zealand studies. There's now so much evidence of
an associaiton between teen's marijuana use and later psychosocial
problems that it's hard to dismiss the likelihood of a causal effect,
Kleber argues. "Macleod's team sees the smoke but won't acknowledge
that there's a fire," he says.

The controversy continues to smolder. The new review of research
results "confirms what's been known for decades about marijuana's lack
of extreme harmfulness," remarks medical sociologist Marsha Rosenbaum,
director of the Drug Policy Alliance's San Francisco office. Her
organization works to decriminalize marijuana but doesn't condone its
use by teenagers.

On the other hand, David Murray, special assistant to the director of
the Office of National Drug Control Policy in Washington, D.C.,
argues that reports of teens often developing psychological or
behavioral difficulties after beginning to smoke marijuana are reason
enough to regard early use of the drug as a public health concern,
especially given the increased potency of marijuana sold in the
United States in recent years.