Cannabis plant
A cannabis plant is pictured during a gathering demanding the legalisation of cannabis in Athens' Syntagma Square, May 9, 2015. Reuters/Kostas Tsironis

A 25-year University of Lausanne study has revealed the long-term effects of smoking marijuana. It says if one smokes cannabis over a long period of time, it does have an effect on the person’s verbal and short-term memory. The smoker may forget more words compared to someone who doesn’t smoke or smokes very little.

Lead researcher Prof. Reto Auer studied the marijuana habits of 3,500 Americans over a 25-year period. Auer and his team followed thousands of young adults into their middle age and discovered that long-term cannabis use is linked to poorer performance on verbal memory tests.

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The researchers started the study, now published in JAMA Internal Magazine, in the mid 80s and the participants were aged 18-30 years. The research looked at a test of verbal memory and repeated measures of marijuana exposure. It examined how a participant processed executive function and speed.

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Out of 3,499 participants, more than 80 percent admitted to smoking cannabis during the first year of the study. However, interestingly, 25 years later, only 12 percent continued smoking in the middle age.

The results showed that for every five years of marijuana exposure, a user remembered a word less from a list of 15, compared to one who never smoked at all, writes

“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,” said Auer.

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Almost 35 percent of people aged 14 years and above have used cannabis one or more times in their life in Australia. According to Dr. Peter Gates, senior research officer at National Cannabis Prevention and Information Centre, cannabis in Australia is a concern as any impact on a person’s cognition is unwanted.

“We know that a user who stops smoking cannabis will see positive cognitive effects within the month, like working memory, attention span, ability to learn and blood flow in brain,” Gates added.