Scientists have identified a likely mechanism by which cocaine use can cause brain damage and decreased cognitive function. Using advanced brain imaging techniques, scientists have clearly demonstrated for the first time that cocaine use temporarily narrows blood vessels in the human brain. In addition, this study shows that repeated cocaine use has a cumulative effect, where the more an individual uses the drug, the more it causes blood vessel narrowing. These findings suggest that heavy users may be more susceptible to cocaine causing strokes, bleeding inside the brain, thinking and memory deficits, and other brain disorders.
The study conducted by scientists at McLean Hospital and Harvard Medical School in Boston, will appear in the February 4, 1998, issue of the Journal of the American Medical Association.
Dr. Alan I. Leshner, Director of the National Institute on Drug Abuse (NIDA), which funded the study, commented, "This study shows changes that cocaine can cause in blood vessels in the human brain and it suggests the mechanism by which cocaine has some of its most devastating effects. The study also suggests a target for developing better treatments to protect against or reverse some of cocaine's actions."
Using an imaging technique called magnetic resonance angiography, in a double-blind study, the investigators administered two relatively low doses of cocaine or a placebo to 24 men, ages 24 to 34. The men were experienced cocaine users but were otherwise medically healthy.
Images of the brain were taken before and 20 minutes after cocaine was administered. The scans showed that five of eight men who received the higher of the two doses (0.4 mg per kg of body weight) showed constricted blood vessels in the brain. The changes ranged from small differences in the structure of brain arteries to major narrowing and other changes in arterial structure. In contrast, brain scans of only three of nine subjects who received half that amount of cocaine showed any blood vessel changes, and only one of seven men who received the placebo showed abnormalities.
Importantly, the more often the men had used cocaine in the past, the greater the chance that cocaine would constrict their brain arteries. This finding suggests that cocaine has a cumulative effect in narrowing the brain's blood vessels. "While additional studies will be needed to clarify the details of this relationship, the current data suggest that the incidence of cocaine-induced vasoconstriction, with its potentially harmful consequences, may be increased in individuals who escalate from occasional to regular cocaine use," said research team leader Dr. Marc J. Kaufman of McLean Hospital.