112 lines
5.6 KiB
Plaintext
112 lines
5.6 KiB
Plaintext
THREE THINGS MARIJUANA DOESN'T DO from California NORML Reports, April 1992
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(1) NO BRAIN DAMAGE SEEN IN MARIJUANA-EXPOSED MONKEYS
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Two new scientific studies have failed to find evidence
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of brain damage in monkeys exposed to marijuana, undercutting
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claims that marijuana causes brain damage in humans.
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The studies were conducted by two independent
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research groups. The first, conducted by Dr. William Slikker,
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Jr. and others at the National Center for Toxicological Research
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in Arkansas examined some 64 rhesus monkeys, half of which
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were exposed to daily or weekly doses of marijuana smoke for
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a year. The other, by Gordon T. Pryor and Charles Rebert at SRI
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International in Menlo Park, California, which is still
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unpublished, looked at over 30 rhesus monkeys that had inhaled
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marijuana one to three times a day over periods of 6 to 12
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months. Neither study found evidence of structural or
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neurochemical changes in the brains of the monkeys when
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examined a few months after cessation of smoking.
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The new results cast doubt on earlier studies
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purporting to show brain damage in animals. The most famous
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of these was a study by Dr. Robert Heath, who claimed to find
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brain damage in three monkeys heavily exposed to cannabis.
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Heath's results failed to win general acceptance in the
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scientific community because of the small number of subjects,
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questionable controls, and heavy doses.
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Subsequent rat experiments by Dr. Slikker and others
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reported persistent structural changes in the brain cells of
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rats chronically exposed to THC. The studies did not show that
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pot kills brain cells, as alleged by some pot critics, but they
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did show degeneration of the nerve connections between brain
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cells in the hippocampus, where THC is known to be active.
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Although scientists have regarded the animal evidence
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as inconclusive, some critics have cited it as proof that pot
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causes brain damage in humans. Thus Andrew Mecca, the
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director of California Department of Alcohol and Drug Abuse,
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recently stated on the Ron Reagan, Jr. talk show (Sep. 2, 1991)
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that marijuana "leaves a black protein substance in the
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synaptic cleft" of brain cells, a claim apparently based on
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Heath's monkeys. When asked by a NORML member for his
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evidence, Mecca sent a list of three references, none of which
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turned out to have anything to do with brain damage.
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Although the new monkey studies found no physical
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brain damage, they did observe behavioral changes from
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marijuana. Slikker's group found that monkeys exposed once a
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day to the human equivalent of four or five joints showed
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persistent effects throughout the day. Slikker says that the
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effects faded gradually after they were taken off marijuana,
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and were not detectable seven months later, when they were
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sacrificed. Autopsies did reveal lingering chemical changes in
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the immune cells in the lungs of monkeys that had inhaled THC.
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However, Slikker's group concluded that experimental exposure
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to marijuana smoke "does not compromise the general health of
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the rhesus monkey."
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References:
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William Slikker, Jr. et al, "Chronic Marijuana Smoke Exposure in the Rhesus
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Monkey," Fundamental and Applied Toxicology 17: 321-32 (1991)
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Guy Cabral et al, "Chronic Marijuana Smoke Alters Alveolar Macrophage
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Morphology and Protein Expression, Pharmacology Biochemistry and
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Behavior 40: 643-9 (1991)
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Merle Paule et al., "Chronic Marijuana Smoke Exposure in the Rhesus Monkey
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II: Effects on Progressive Ratio and Conditioned Position
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Responding," Journal of Pharmacology and Experimental Therapeutics
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260: 210-22 (1992)
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(2) POT FOUND NOT TO CAUSE FETAL ALCOHOL SYNDROME
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A new study of children born to marijuana-smoking
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mothers found no link between marijuana exposure and the
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birth defects of fetal alcohol syndrome (FAS). The new study,
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by Dr. Susan J. Astley of the University of Washington,
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published in the January, 1992 issue of Pediatrics,
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contradicted a 1982 study by Dr. Ralph Hingson, in which
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prenatal exposure to marijuana was found to increase the risk
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of FAS.
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Hingson's results, which have not been replicated, have
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been questioned on various methodological grounds, in
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particular the difficulty of controlling for combined drinking
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and pot use.
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The new study looked for facial deformities
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symptomatic of FAS in 40 children whose mothers had smoked
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marijuana heavily during pregnancy and 40 controls, It found no
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association between marijuana and FAS, but deformities were
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observed in children of women who drank 2 ounces of alcohol
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per day or took cocaine.
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(3) NEW STUDY FINDS POT DOESN'T LOWER TESTOSTERONE
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A new study by Dr. Robert Block at the University of
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Iowa disputes the commonly held notion that marijuana alters
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the level of testosterone and other sex hormones.
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The study contradicted a widely publicized 1974 study
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by Dr. R.C. Kolodony, which reported decreased testosterone
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levels in men who smoked marijuana chronically.
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The U. of Iowa study found that chronic marijuana use
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had no effect on testosterone, luteinizing hormone, follicle
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stimulating hormone, prolactin and cortisol in men or women.
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Noting that six other studies had failed to show
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lowered testosterone levels in men, Dr. Block concluded: "It
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appears that marijuana, even heavy use of the kind that's
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typical in the United States, doesn't alter testosterone levels."
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However, he cautioned that heavy use might have other
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adverse effects, including "possible effects on reproductive
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function and mild, selective cognitive impairments associated
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with heavy, chronic use."
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Block's study is published in Drug and Alcohol
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Dependence, Vol. 28: 121-8 (1991).
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