EXPERT DISCUSSES RISKS, BENEFITS OF MARIJUANA USE

WASHINGTON -- Last week, the Justice Department ordered its staff to
back off prosecution of people who use marijuana for medical purposes
in the 14 states in which such use is legal. The directive reopened a
question that has been part of the debate on U.S. drug policy for decades.

To understand more about the drug's medical properties, we turned to
Daniele Piomelli, who since 1998 has led a program, funded by the
National Institutes of Health, to study the impact of marijuana and
other psychoactive drugs on the brain. He is a professor of
pharmacology and biological chemistry at the University of California
at Irvine and director of the center for Drug Discovery and
Development at the Italian Institute of Technology in Genoa.

Q: What medical benefits does marijuana offer? Have these benefits
been demonstrated in rigorous scientific studies?

A: Several controlled clinical trials have been carried out in the
last few years, using either smoked marijuana or a mouth spray that
contains an extract of the marijuana plant. The results are quite
consistent. They show that marijuana improves the well-being of
patients with multiple sclerosis and alleviates chronic pain in
patients with damage or dysfunction of nerve fibers (so-called
neuropathic pain). Other work has shown that marijuana and its active
ingredient THC (delta-9-tetrahydrocannabinol) reduce the nausea that
accompanies chemotherapy, stimulate appetite in AIDS wasting syndrome
and lessen tics in Tourette's syndrome. By and large, the use of
marijuana in these trials was associated with few and mild side
effects (for example, dry mouth and memory lapses).

Q: What are the risks of medical use of marijuana? Could it become
addictive or lead to use of other, more dangerous drugs?

A: Marijuana can produce dependence, though less aggressively than,
say, tobacco or the so-called opiate painkillers. Frequent use is
risky, however, particularly during adolescence when the neural
circuits in the brain are still maturing. It turns out that the brain
employs its own marijuana-like substances, called endocannabinoids, to
send signals from one neural cell to another, and that THC mimics
these substances. The endocannabinoids seem to be very important in
brain development, so messing with them before the nervous system
becomes fully mature is not a smart thing to do.

There is little hard evidence that using marijuana leads to the
subsequent use of other addictive drugs. On the other hand, it is
becoming increasingly clear that stressful life events (particularly
in critical periods such as adolescence) can encourage drug use and
facilitate the development of addictions.

Q: How would a marijuana user be sure to get the correct dose of the
active ingredient?

A: It is difficult to say, because the various types of marijuana now
available contain widely different concentrations of THC. Standardized
marijuana preparations that contain a fixed amount of THC are not
currently sold to the public, though the National Institute on Drug
Abuse does provide them to investigators for use in clinical trials.