DRUG IMPAIRS COORDINATION

Marijuana use triggers distinct changes in behavior and coordination,
alterations that also have effects on perceptions of distance and time,
experts said yesterday.

Coordination is a central motor ability that becomes impaired, doctors say,
because the drug forces a relaxation of the muscles. The more marijuana
that is inhaled, studies show, the longer the drug-induced relaxation
lasts. This in turn leads to slowed reactions and compromising of spatial
judgments.

A 1997 study of student athletes by the National Collegiate Athletic
Association found that marijuana use by the students not only caused a lack
of coordination but also impaired speech, a loss of critical thinking and
problems with short-term memory. Because the drug has its most profound
effects on vital chemical pathways in the brain, doctors found that it can
have a substantial impact on mental health.

"The plant product now is very potent, and we see a fair number of people
showing up in our hospital with psychosis," said Dr. Thomas Newton, medical
director of the addiction program at the University of California, Los Angeles.

Within minutes of taking a drag on a marijuana cigarette, Newton said, the
drug's active ingredient, tetrahydrocannabinol - THC - floods the
bloodstream, impairing several key chemical pathways, particularly the
dopamine-producing neurons in the brain. These neurons play a major role in
coordination. The dopamine system is altered in certain disorders, such as
Parkinson's disease, in which people lose the ability to walk with a smooth
gait.

Studies by the National Institutes of Health have suggested that the lack
of coordination helps explain why people who smoke marijuana and then take
to the wheel are so often involved in automobile accidents.

One of those studies showed that 32 percent of injured drivers in a
Baltimore hospital's shock-treatment unit had measurable levels of THC in
their blood.

Newton said the drug on the streets today is at least 12 times more potent
than the marijuana smoked 20 years ago. The result can be a more dramatic
psychosis than doctors used to treat. "We have certainly had cases in which
people don't get better all that quickly."

Marijuana is mildly addictive physically, he said, but the psychological
desire to have it can become overwhelming. Continuous use, he added, leads
to so demanding a desire that smokers "will spend all of their money just
to get stoned."