Long-Term Marijuana Use Linked to Poor Verbal Memory in Middle Age

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A new research published Feb.1 in the journal JAMA International Medicine suggests that long-term marijuana can potentially do permanent damage to your short-term memory. They found that people who smoke pot have poor verbal memory by the time they reach middle age.

Reuters reports that a team of researchers led by Professor Reto Auer of the University of Lausanne in Switzerland examined data on marijuana habits of almost 4,500 young Americans over a 25-year period to explore the potential long-term impact of marijuana use. At the end of the study, the subjects were given standardized tests of verbal memory, processing speed and executive function.

The subjects were aged 18 to 30 at the beginning of the study that took place in 1985 and 1986, reports Philly. The participants were residents of Alabama, Chicago, Minneapolis and California. Almost 85 percent of the participants admitted to smoking marijuana in the past while 12 percent admitted smoking pot into middle age.

The testing covered verbal memory measured by the ability to memorize and recall a list of 15 words, visual motor, working memory, sustained attention skills and the ability to problem-solve and plan.

The results show that, as past years of marijuana increased, verbal memory scores decreased. Those middle-aged participants who were marijuana smokers in the past fared worse in terms of verbal memory and mental-processing speed. In simple terms for every five years of exposure, 50 percent of marijuana users would forget one word from a list of 15 words.

"Recreational marijuana users use it to get high, to benefit from the transient change it produces," Auer told Reuters Health by email. "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."

Same results were generated after accounting for a range of factors including smoking, drinking and drug use, exercise habits, depression history, blood pressure and cholesterol levels, reports Philly.

However, researchers emphasized that lifetime exposure level does not affect other skills that were tested.

In the past, several studies have found that people who smoke marijuana on a daily basis over the years were found to perform worse on various cognitive tasks compared to others who have not used or have used it less frequently for shorter periods and then stopped, according to Wayne Hall of the University of Queensland, Australia.

"Cannabis is a drug, and like all drugs, it can harm some users when they use it in particular ways. This study adds to the substantial evidence that the daily use of cannabis over periods of years and decades can harm the mental and physical health of people who use it in this way," Wayne said.

Check out the other effects of marijuana to your memory with the video from dailyRx: