THERE'S GOOD NEWS FOR moderate smokers in the latest research on marijuana
and bad news for heavy smokers. Getting caught or causing an accident while
stoned are still the greatest dangers, but those who smoke marijuana on a
weekly or daily basis over several years risk potentially serious damage to
some mental faculties and to their lungs. Adolescents who are heavy pot
smokers may retard their emotional and intellectual development.

Pot creates a high by affecting strategic locations in the brain, including
the hippocampus, where linear thinking takes place; the rostral
ventromedial medulla, at the base of the brain, which modulates the
intensity of pain sensations; and the cerebellum, which coordinates
movement and balance. Until recently, no one understood how marijuana
penetrates the brain.

Then, in 1992, a Hebrew University team discovered chemicals in the brain
that are similar to cannabinoids, the class of chemicals contained in
marijuana. These newly discovered chemicals, called anandamides, may block
pain and help regulate sleep patterns. THC (delta-g-tetrahydrocannabinol),
the marijuana ingredient most responsible for altering consciousness, uses
the same docking station in brain cells as anandamides do. Pot defender Dr.
John P. Morgan, co-author of Marijuana Myths, Marijuana Facts, says that
THC merely "borrows a prepared pathway"; that is, it makes use of a
functioning system without contaminating it. Pot foe Dr. Robert DuPont,
former head of the National Institute on Drug Abuse, says that THC
"pirates" the brain's communication network. By that, DuPont means that pot
users are allowing THC to steal cell receptors that should be used only by
the brain's chemicals and are risking permanent changes to the brain.

Repeated studies of long-term, heavy pot smokers in Costa Rica have yielded
no convincing evidence that smokers are slower thinkers than nonsmokers.
And Dr. Andrew Weil, author of the first double-blind human experiments
with marijuana, in 1968, contends that "whatever changes may occur in
mental function associated with marijuana use, they will all reverse if you
get people away from it." However, studies in India, Europe and the U.S.
have found that heavy use brings an increased risk of potentially permanent
short-termmemory loss and may hinder the ability to adapt to new rules and
situations.

While the question of whether or not pot inflicts permanent damage remains
unresolved, scientists agree that pot has temporary cognitive effects. In a
recent study, researchers at McLean Hospital, in Belmont, Massachusetts,
found that mental function in heavy users was inhibited for twenty-four
hours after subjects had smoked pot, long after the high was gone. If you
smoke pot regularly and don't notice any problems, then you may not be
suffering any damage at all - or you may have adjusted to a lower
intellectual standard.

Marijuana has been ranked with caffeine in addictiveness potential -
considerably lower than alcohol, nicotine or cocaine. About one in every
eleven people who try pot becomes a chronic, heavy user for a time. Most
seem able to stop at will. Those who do become dependent on marijuana
sometimes undergo a form of withdrawal when they abstain. A credible study
by psychiatrists at the University of California at San Diego documented
withdrawal symptoms in about sixteen percent of their study subjects, who
had all used pot daily for an average of almost seventy months. These
symptoms included nervousness, tension, restlessness, sleep disturbance and
appetite changes.

"Smoking pot every third Saturday night isn't going to damage you in a
measurable way, unless you do something stupid when you're stoned," says
Mark Kleiman, a drug policy expert at the University of California at Los
Angeles. The hidden risk is that "you won't be able to keep it to every
third Saturday night."

Marijuana smoke contains many of the same toxic chemicals as tobacco smoke,
including carcinogens such as tar, carbon monoxide and cyanide. Occasional
pot users do not generally inhale enough smoke to affect the linings of the
trachea and bronchial tubes. Heavy users, however, often experience the
respiratory problems that pack-a-day cigarette smokers do, such as chronic
bronchitis and exacerbation of asthma.

The largest cohort of people using pot on a regular, long-term basis in the
U.S. began smoking in the Sixties, so they haven't yet reached the age when
cancers manifest with a vengeance. Small-scale studies of chronic pot
users' lungs have revealed abnormal changes in bronchial cells, indicating
an increased risk of cancer, and many scientists believe that pot's
lung-cancer risk could prove to be comparable to that of cigarettes.

Long-term use of marijuana may lower sperm counts in men and may interfere
with menstrual cycles in women. According to Buzzed, a comprehensive guide
to alcohol and illicit drugs produced by the Duke University Medical
Center, pot "suppresses the production of hormones that help to regulate
the reproductive system." The scientific literature does not give a clear
message that these disruptions are severe enough to affect fertility.

Pregnant women, however, should avoid marijuana: There is some evidence
thatbabies born to pot smokers may have a reduced birth weight or worse.
According to November's Lancet article by Wayne Hall and Nadia Solowij,
"Infants exposed in utero to cannabis [may] show behavioral and
developmental effects during the first few months after birth. Between the
ages of four and nine years, exposed children have showed deficits in
sustained attention, memory and higher cognitive functioning."

CAN POT CURE A HEADACHE?

"In the 1970s and 1980s, drug companies such as Eli Lilly were very excited
about the medical uses of marijuana," says Dr. John Morgan, "before the War
on Drugs escalated and they gave up." One of the exciting discoveries in
pot research - most of which is being conducted in Europe - is that
cannabinoids probably have painkilling properties; there are some reports
that they could be useful in alleviating migraines They also may work as
antioxidants, thus reducing brain swelling in stroke and head-trauma
victims. Pot is now used regularly - often illegally - to reduce the need
for morphine, to counteract nausea and to stimulate appetite in people with
wasting diseases like AIDS.