Myth: Marijuana Kills Brain Cells

Used over time, marijuana permanently alters brain structure and function, causing memory loss, cognitive impairment, personality deterioration, and reduced productivity.

Fact: None of the medical tests currently used to detect brain damage in humans have found harm from marijuana, even from long term high-dose use. An early study reported brain damage in rhesus monkeys after six months exposure to high concentrations of marijuana smoke. In a recent, more carefully conducted study, researchers found no evidence of brain abnormality in monkeys that were forced to inhale the equivalent of four to five marijuana cigarettes every day for a year. The claim that marijuana kills brain cells is based on a speculative report dating back a quarter of a century that has never been supported by any scientific study.

• Heath, R.G., et al. “Cannabis Sativa: Effects on Brain Function and Ultrastructure in Rhesus Monkeys.” Biological Psychiatry 15 (1980): 657-690.

Ali, S.F., et al. “Chronic Marijuana Smoke Exposure in the Rhesus Monkey IV: Neurochemical Effects and Comparison to Acute and Chronic Exposure to Delta-9-Tetrahydrocannabinol (THC) in Rats.” Pharma