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THREE THINGS MARIJUANA DOESN'T DO from California NORML Reports, April 1992


   Two new scientific studies have failed to find evidence 
of brain damage in monkeys exposed to marijuana, undercutting 
claims that marijuana causes brain damage in humans.
    The 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unpublished, looked at over 30 rhesus monkeys that had inhaled 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.
   The 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.  
   Subsequent 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.   
   Although 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.
   Although the new monkey studies found no physical 
brain damage, they did observe behavioral changes from 
marijuana.  Slikker's group found that monkeys exposed once a 
day to the human equivalent of four or five joints showed 
persistent effects throughout the day.  Slikker says that the 
effects faded gradually after they were taken off marijuana, 
and were not detectable seven months later, when they were 
sacrificed.  Autopsies did reveal lingering chemical changes in 
the immune cells in the lungs of monkeys that had inhaled THC.   
However, Slikker's group concluded that experimental exposure 
to marijuana smoke "does not compromise the general health of 
the rhesus monkey."


William Slikker, Jr. et al, "Chronic Marijuana Smoke Exposure in the Rhesus
	Monkey," Fundamental and Applied Toxicology  17: 321-32 (1991)

Guy Cabral et al, "Chronic Marijuana Smoke Alters Alveolar Macrophage
	Morphology and Protein Expression, Pharmacology Biochemistry and
	Behavior 40: 643-9 (1991) 

Merle Paule et al., "Chronic Marijuana Smoke Exposure in the Rhesus Monkey
	II: Effects on Progressive Ratio and Conditioned Position
	Responding," Journal of Pharmacology and Experimental Therapeutics
	260: 210-22 (1992) 


   A 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 
of FAS. 
    Hingson's results, which have not been replicated, have 
been questioned on various methodological grounds, in 
particular the difficulty of controlling for combined drinking 
and pot use.   
   The 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.


   A 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.
   The study contradicted a widely publicized 1974 study 
by Dr. R.C. Kolodony, which reported decreased testosterone 
levels in men who smoked marijuana chronically.
   The U. of Iowa study found that chronic marijuana use 
had no effect on testosterone, luteinizing hormone, follicle 
stimulating hormone, prolactin and cortisol in men or women. 
   Noting 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."  
   However, he cautioned that heavy use might have other 
adverse  effects, including "possible effects on reproductive 
function and mild, selective cognitive impairments associated 
with heavy, chronic use."
   Block's study is published in Drug and Alcohol 
Dependence, Vol. 28: 121-8 (1991).