A recent study by Duke University has found that people repeatedly diagnosed with marijuana dependence during young adulthood had noticeable declines in IQ scores by age 38, especially when the heavy use started in their teens.
The study published online in Proceedings of the National Academy of Sciences, found a small to medium decline in mean IQ between tests taken on the eve of adolescence and again at age 38 was seen in those diagnosed at least three times with marijuana dependence, according to Madeline Meier, PhD, of Duke University, and colleagues, who reported on data from 1,037 participants in a New Zealand birth cohort.
In the small group of participants who became marijuana dependent before age 18 — a total of 23 cohort members — the decline translated to an average of about 8 IQ points, whereas 14 participants who also showed heavy marijuana use but only beginning in adulthood showed only a very small drop in full-scale scores. The researchers also reported that the size of the mean decline increased with the number of marijuana dependence diagnoses that participants had received in five evaluations conducted from ages 18 to 38.
The study findings are consistent with speculation that marijuana use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects.
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why must we always tell parents what marijuana does long term to their kids. I think its time to focus on all the man made drugs these parents shove down their kids throat. My youngest just got out of high school over more than his friends were on a presciption drug.. More n more parents putting kids on these drugs to be able to handle their own kids. I think its time for researchers and other to tell people about long term effects do to these drugs, cause you’ll find out that all these drugs your doctor gives your kid is much worse than marijuana. Legal or not legal drugs should all be talked trash on, but no you never hear nbc or here or anyother place talking about all the rest just the ellegal ones. Time for man made drugs to be desputed more of them than ellegal ones. Wake up world.