Marijuana Causes Brain Damage

    Government experts now admit that pot doesn't kill brain cells.(1) This myth came from a handful of animal experiments in which structural changes (not actual cell death, as is often alleged) were observed in brain cells of animals exposed to high doses of pot. Many critics still cite the notorious monkey studies of Dr. Robert G. Heath, which purported to find brain damage in three monkeys that had been heavily dosed with cannabis. In 1974, Dr. Heath strapped facemasks to monkeys and forced them to inhale the equivalent of 63 joints, in just 5 minutes. The monkeys were sacrificed 3 months later, and Dr. Heath claimed that because of the marijuana, the monkeys suffered brain damage.(2)

The Red Cross Water Safety manual states that 3 to 5 minutes without oxygen can cause brain damage.(7) The false statement accusing marijuana of causing brain damage is still around today, even though the test was re-done in 1992, more accurately, and did not show Marijuana to cause any brain damage. This work was never replicated and has since been discredited by a pair of better controlled, much larger monkey studies, one by Dr. William Slikker of the National Center for Toxicological Research(3) and the other by Charles Rebert and Gordon Pryor of SRI International.(4) Neither found any evidence of physical alteration in the brains of monkeys exposed to daily doses of pot for up to a year. Human studies of heavy users in Jamaica and Costa Rica found no evidence of abnormalities in brain physiology.(5) Even though there is no evidence that pot causes permanent brain damage, users should be aware that persistent deficits in short-term memory have been noted in chronic, heavy marijuana smokers after 6 to 12 weeks of abstinence.(6) It is worth noting that other drugs, including alcohol, are known to cause brain damage.

If it doesn't kill brain cells, how does it get you `high'?

    Killing brain cells is not a pre-requisite for getting "high".  Marijuana contains a chemical which substitutes for a natural brain chemical, with a few differences. This chemical touches special "buttons" on brain cells called "receptors."  Essentially, marijuana "tickles" brain cells. The legal drug alcohol also tickles brain cells, but it will damage and kill them by producing toxins (poisons) and sometimes mini-seizures.(8) Also, some drugs will wear out the buttons which they push, but marijuana does not, and the receptors re-active once there is no more THC available.(9)

Sources:

1. Dr. Christine Hartel, Acting Director of Research, National Institute of Drug Abuse, cited by the State of Hawaii Dept of Health, Alcohol and Drug Abuse Division in memo of Feb. 4, 1994.

2. For an overview, see NAS Report, op. cit., pp. 81-2. R.G. Heath et al, Cannabis sativa: effects on brain function and ultrastructure in Rhesus monkeys, Biol. Psychiatry 15: 657-90 (1980).

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

4. Charles Rebert & Gordon Pryor - Chronic Inhalation of Marijuana Smoke and Brain Electrophysiology of Rhesus Monkeys, International Journal of Psychophysiology V 14, p.144, 1993.

5. NAS Report, pp. 82-7.

6. Cannabis and Memory Loss, (editorial) British Journal of Addiction 86: 249-52 (1991).

7. Red Cross Water Safety Manual.

8. "Structure of a Cannabinoid Receptor" by L. A. Matsuda , S. J.
Lolait , M. J. Browstein, A. C. Young, T. I. Bonner in "Nature" Vol.
346 Iss. 6824 pp. 561-564. August, 1990.

9. "Chronic Exposure to Delta-9-Tetrahydrocannabinol Fails to
Irreversibly Alter Brain Cannabinoid Receptors" by Tracy M. Westlake,
Allyn C. Howlett, Syed F. Ali, Merle G. Paule, Andrew C. Scallet,
William Slikker Jr. in ``Brain Research'' Vol. 544 pp. 145-149. 1991.