Smoking Cannabis before 18 lowers IQ

marijuana and the BrainSmoking Marijuana lowers your IQ according to a new study.A recent study from New Zealand shows young cannabis smokers are doing real and irreversible damage to their brains.

The study followed about 1,000 people for over 20 years and found that those who smoked cannabis at least four times a week through their teens and 20s had a noticeable decline in IQ. The more people smoked, the greater this decline.



The study found that those with the greatest loss of IQ started regularly smoking cannabis before they turned 18. When these people decreased their cannabis use or stopped entirely, they were not able to fully recover their lost IQ.

As a part of their article in the US journal Proceedings of the National Academy of Sciences, the researchers said, "Collectively, these findings are consistent with speculation that cannabis use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects."

In simple terms, that means cannabis is harmful to young people because their brains are still developing. If you introduce cannabis at this stage, it can disrupt this development and negatively impact the user.

On average, the people who started smoking cannabis as an adolescent, and continued smoking for years lost eight IQ points.

One of the researchers, Prof Terrie Moffitt of King's College London's Institute of Psychiatry, said, "This work took an amazing scientific effort. We followed almost 1,000 participants, we tested their mental abilities as kids before they ever tried cannabis, and we tested them again 25 years later after some participants became chronic users.”

He said the study was very special because it covered such a long period of time and included very accurate information about peoples drug use. The study also took into account peoples drinking habits and any other drugs they were taking.

Moffitt concluded that, “I'm fairly confident that cannabis is safe for over-18 brains, but risky for under-18 brains."

Colleague Professor Robin Murray, from the Institute of Psychiatry, said: "We have known for some time that heavy use of cannabis increases risk of schizophrenia-like psychoses but this remains a relatively rare outcome so it's not so important from a public health point of view. There are far fewer studies on its effect on minor psychiatric illness or on everyday life. However, there are a lot of clinical and educational anecdotal reports that cannabis users tend to be less successful in their educational achievement, marriages and occupations.”

Rurray added, "It is of course part of folk-lore among young people that some heavy users of cannabis - my daughter callers them 'stoners' - seem to gradually lose their abilities and end up achieving much less than one would have anticipated. This study provides one explanation as to why this might be the case."

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