Bad news for mary-jane lovers, according to a new study published online by JAMA Internal Medicine, people who smoked weed regularly as teenagers remembered fewer words as they entered middle age.
A study was conducted, starting with 5000 young adults between 18 and 35, monitoring them over the course of 25 years. At the end of the study, 3,400 subjects remained and the test results started pouring in.
Tests were conducted to measure cognitive function, using standardized verbal memory, processing speed and function tests.
The study found that current marijuana users scored lower on verbal memory and processing speed. Longtime users showed poor results on all three: memory, speed and function.
According to the study, test subjects were also asked to memorize a list of fifteen words. The claim is that for every five years of marijuana use, the test subject remembered one fewer word from the list.
Past users typically experienced some loss in verbal memory skills, though marijuana use doesn’t seem to affect other skills.
A similar study from New Zealand also found that frequent marijuana use over a long term affects IQ as well. The study tested subjects at age 13, and again 25 years later at 38. Subjects with at least five years of use showed noticeably lower IQ scores.
The study authors say that this kind of information is critical while many states in the U.S. decriminalize marijuana.
Wayne Hall of the Center for Youth Substance Abuse Research at the University of Queensland in Australia and Michael Lynskey of the National Addiction Centre at King’s College London explain the importance of these studies:
“Young adults may be skeptical about advice on the putative adverse health effects of marijuana, which they may see as being overstated to justify the prohibition on its use. More research on how young people interpret evidence of harm from marijuana and other drugs would be useful in designing more effective health advice.”
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