Marijuana, Memory and Middle Age

Prolonged use of marijuana associated with memory loss in middle age


Smoke a little pot, now and then? Don't go overboard, it might affect your memory.

Researchers in Lausanne, Switzerland, found that prolonged use of marijuana can result in verbal memory loss during middle age.

Lead author Reto Auer, MD, MAS, commented in an email for an article published byReuters Health, “Recreational marijuana users use it to get high, to benefit from the transient change it produces. But this transient effect might have long term consequences on the way the brain processes information and could also have direct toxic effects on neurons.”

Dr. Auer is a primary care physician and researcher at the University of Lausanne in Switzerland.

As medical marijuana and legalized marijuana use becomes more common, researchers are looking into long-term effects.

Dr. Auer and colleagues studied data from a long-running study of US adults. The study began in the 1980s and continued for 25 years.

Data collected for the study included marijuana use. Study participants also took standardized tests of verbal memory, mental processing speed and executive functions. Executive functions are the decision-making and judgment processes in the brain.

Almost 3,400 study participants completed the standardized tests at the beginning and end of the research period.

Study participants were 18 to 30 years old in the 1980s. Eighty percent of them reported marijuana use. Only 12 percent continued to use marijuana into middle age.

Dr. Auer and colleagues found that people who used more marijuana scored more poorly on verbal memory tests than those who used little or none. They determined that for every five years of marijuana exposure, half the marijuana users would remember one less word in a 15-word list.

Dr. Auer and team did not find any effects of marijuana use on mental processing speed or executive function.

The study was published in the January issue of the Journal of the American Medical Association.

Information on study funding and conflict of interest was not available at the time of publication.