New Study Suggests Marijuana Has An Adverse Effect On Memory


New study shows that long-term smoking of marijuana will have a negative effect on the smoker’s verbal memory, that is, the ability to remember words. The study showed that for every five years on average, one in two pot smokers remember one word less from a list of 15 words.

To carry out the purpose of the research, the researchers studied members who were enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. This study included 5,000 or more adults between ages 18-30. The participants were always asked if they had used marijuana in the previous meeting during follow-up visits by the researchers.

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While most were not heavy smokers, about About 84% had smoked pot at some point over the years and many had quit by the time they were middle-aged. Only  about 11% remained active smokers. After 25 years of the investigation, the participants’ abilities were tested for verbal memory, processing speed and executive function.

The participants’ performances worsened in all three tests. The results, however, were tweaked by other factors such as; use of other substances and depression, finding only the relation between marijuana and decrease of verbal memory to be valid.

“We found a dose-dependent independent association between cumulative lifetime exposure to marijuana and worsening verbal memory in middle age,” the researchers wrote in the study which was  published on February 1 in the journal JAMA Internal Medicine.

There were some limitations to the research as reported in the journal. The marijuana use was self reported, that is, no extra tests were carried out to determine if the participant had indeed smoked some or not. Also, prior to the research, there was no specific data to determine the cognitive abilities of the participants. That is, one can’t tell if the participants were originally dull and if people with dull cognizance are likely to use marijuana more.

The impact of marijuana on health has been somewhat unclear over the years and this has caused legalization battles where the plant is concerned. The researchers do believe that long-term use of marijuana will have a negative effect on the health of its users, and there are also various long running researches (like the one in New Zealand) that proves this.

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