Myths about cannabis smoke killing brain cells stem from a study undertaken by Dr. Robert Heath for Tulane University in 1974. The study was widely quoted by then-Governor of California, Ronald Reagan, as proof that cannabis use causes brain damage in humans.
This study was thoroughly reviewed by a distinguished panel of scientists sponsored by the Institute of Medicine and the National Academy of Sciences. Their results were published under the title, Marijuana and Health in 1982. Heath's work was sharply criticized for its insufficient sample size (only four monkeys), its failure to control experimental bias, and the misidentification of normal monkey brain structure as "damaged".
Heath's report was also made public at a U.S. Senate subcommittee hearing investigating marijuana and health. Dr. Julius Axelrod, who received the Nobel Prize in 1970 for his work on the effects of drugs on the brain, was asked to evaluate the Heath study.
He told the senators that the amount of smoke inhaled by the monkeys was equivalent to a human being smoking over a hundred marijuana cigarettes each day for six months. "The results indicate that marijuana causes an irreversible damage to the brain," said Axelrod. "But the amounts used are so large that one wonders whether it's due to the large toxic amounts Dr. Heath has given." A large enough dose of any substance will produce negative results in animals or human beings, said Axelrod, who believed that Heath should have administered doses of varying degrees to determine which effects would have been produced by different levels of marijuana.
Lester Grinspoon, another critic of the Heath study, points out that the monkeys in the experiment were forced to ingest excessive amounts of marijuana smoke, although a monkey's lung size is only about one-fifteenth as large as that of a human being.
Numerous studies conducted on human populations have been undertaken, yet none have indicated any correlation to cannabis useage and brain damage.
One such study, undertaken at the University of Pennsylvania by a research team headed by Dr. Igor Grant, examined twenty-nine marijuana smokers and an equivalent control group, all of them medical students. Grant and his team administered the most sensitive neurological and neuropsychological tests available and found no appreciable differences when they examined the brains of the students in the two groups.
In 1977, the American Medical Association officially came out in favor of decriminalizing marijuana.That's not the sort of thing you'd expect from the AMA if they believed marijuana caused brain damage, chromosomal abnormalities or any of the other claims alleged by prohibitionists, is it?
While this study has long since been repudiated by the scientific establishment, it is still widely quoted by prohibitionist groups like the Partnership for a Drug Free America, perpetuating the myth that cannabis causes brain damage in humans.
That means that it's up to individuals like you and me to counter the damage caused by outdated, inaccurate, and archaic prohibitionist rhetoric by standing up and talking openly and honestly about cannabis prohibition.
* The work on this page is not my own original writing.
