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THINGS MARIJUANA DOESN'T DO
California NORML Reports, April 1992
NO BRAIN DAMAGE SEEN IN MARIJUANA-EXPOSED MONKEYS
new scientific studies have failed to find evidence of brain damage in monkeys
exposed to marijuana, undercutting claims that marijuana causes brain damage in
studies were conducted by two independent research groups. The first, conducted
by Dr. William Slikker, Jr. and others at the National Center for Toxicological
Research in Arkansas examined some 64 rhesus monkeys, half of which were exposed
to daily or weekly doses of marijuana smoke for a year. The other, by Gordon T.
Pryor and Charles Rebert at SRI International in Menlo Park, California, which
is still unpublished, looked at over 30 rhesus monkeys that had inhaled marijuana
one to three times a day over periods of 6 to 12 months. Neither study found evidence
of structural or neurochemical changes in the brains of the monkeys when examined
a few months after cessation of smoking.
new results cast doubt on earlier studies purporting to show brain damage in animals.
The most famous of these was a study by Dr. Robert Heath, who claimed to find
brain damage in three monkeys heavily exposed to cannabis. Heath's results failed
to win general acceptance in the scientific community because of the small number
of subjects, questionable controls, and heavy doses.
rat experiments by Dr. Slikker and others reported persistent structural changes
in the brain cells of rats chronically exposed to THC. The studies did not show
that pot kills brain cells, as alleged by some pot critics, but they did show
degeneration of the nerve connections between brain cells in the hippocampus,
where THC is known to be active.
scientists have regarded the animal evidence as inconclusive, some critics have
cited it as proof that pot causes brain damage in humans. Thus Andrew Mecca, the
director of California Department of Alcohol and Drug Abuse, recently stated on
the Ron Reagan, Jr. talk show (Sep. 2, 1991) that marijuana "leaves a black protein
substance in the synaptic cleft" of brain cells, a claim apparently based on Heath's
monkeys. When asked by a NORML member for his evidence, Mecca sent a list of three
references, none of which turned out to have anything to do with brain damage.
POT FOUND NOT TO CAUSE FETAL ALCOHOL SYNDROME
new study of children born to marijuana-smoking mothers found no link between
marijuana exposure and the birth defects of fetal alcohol syndrome (FAS). The
new study, by Dr. Susan J. Astley of the University of Washington, published in
the January, 1992 issue of Pediatrics, contradicted a 1982 study by Dr. Ralph
Hingson, in which prenatal exposure to marijuana was found to increase the risk
results, which have not been replicated, have been questioned on various methodological
grounds, in particular the difficulty of controlling for combined drinking and
new study looked for facial deformities symptomatic of FAS in 40 children whose
mothers had smoked marijuana heavily during pregnancy and 40 controls, It found
no association between marijuana and FAS, but deformities were observed in children
of women who drank 2 ounces of alcohol per day or took cocaine.
NEW STUDY FINDS POT DOESN'T LOWER TESTOSTERONE
new study by Dr. Robert Block at the University of Iowa disputes the commonly
held notion that marijuana alters the level of testosterone and other sex hormones.
study contradicted a widely publicized 1974 study by Dr. R.C. Kolodony, which
reported decreased testosterone levels in men who smoked marijuana chronically.
U. of Iowa study found that chronic marijuana use had no effect on testosterone,
luteinizing hormone, follicle stimulating hormone, prolactin and cortisol in men
that six other studies had failed to show lowered testosterone levels in men,
Dr. Block concluded: "It appears that marijuana, even heavy use of the kind that's
typical in the United States, doesn't alter testosterone levels."