A new study conducted by the University of Lausanne, Switzerland says that prolonged use of marijuana can lead to verbal memory loss in middle age, MMJ Observer reports.

Medical marijuana is now easily accessible in almost all the US states.

With the recent reforms proposed to legalize recreational pot, the recent study stressed on more caution on the part of the lawmakers as well as the regular users of weed.

According to the researchers, long time use of pot can damage at least one kind of brain function related to verbal memory tests. However, it does not seem to have any effect on other functions of the brain.

Dr. Reto Auer, lead author of the study, said that they were not expecting an association between chronic cannabis exposure and verbal memory loss.

The study did not employ brain imaging to measure structural changes, the authors note, as reported by Deccan Chronicle.

"Unfortunately, as with all recreational drug exposures, it would not be feasible to perform a long term randomized controlled trial to verify causation," Auer said. "We are left with trying to do the best we can in epidemiological studies and adjust for potential confounders to estimate the potential causal effect of marijuana on health outcomes."

The study indicates that a person consistently exposed to marijuana for long period loses the ability to remember certain words. For every five years of use of marijuana, the researchers found, at least, one or two people could not recall a few words from the 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."

For the study, the researchers analyzed 25-year US study data on young adults. The data included people with repeated exposure to marijuana for prolonged time.

Data from more than 3,500 participants was collected and used for the standardized tests.

The study was published in JAMA Internal Medicine.