Cannabis 'damages teens' IQ'

The major study into the effect of long term and persistent cannabis use has found the drug permanently damages IQ, memory and attention span. The study shows the drug has a different and more damaging effect on teenagers than adults.

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Cannabis study explains why 'users end up achieving less'

Professor Robin Murray from the Institute of Psychiatry at King's College London has called a major study into the effect of long term and persistent cannabis use "very impressive".

Professor Murray said that if the same results were found in other research, public education campaigns should be launched:

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.

It is of course part of folk-lore among young people that some heavy users of cannabis 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.


Teenage brain 'more vulnerable to damage'

New research in to cannabis use has found that persistent and dependent use of the drug before the age of 18 may have a so-called neurotoxic effect, but heavy pot use after 18 appears to be less damaging to the brain. Terrie Moffitt from King's College London said:

It's such a special study that I'm fairly confident cannabis is safe for over-18 brains, but risky for under-18 brains.

Before the age of 18, the brain is still being organised and remodelled to become more efficient and may be more vulnerable to damage from drugs.

Marijuana is 'not harmless, particularly for adolescents'

Researchers found that people who started using cannabis in adolescence and continued for years afterwards showed an average decline in Intelligence Quotient (IQ) test scores of 8 points between the age of 13 and 38.

Madeline H Meier lead a team of researchers who worked with 1,037 people from Dunedin, New Zealand born between 1972/1973. She said an average decline of 8 points may not seem like a lot, but was significant as those with a higher IQ are more like to earn more, have better health and a longer life:

Marijuana is not harmless, particularly for adolescents. Somebody who loses eight IQ points as an adolescent may be disadvantaged compared to their same-age peers for years to come

Teenage cannabis smoking 'permanently damages IQ'

The particular dangers of smoking cannabis are highlighted in the study. Credit: Press Association

Teenagers who regularly smoke cannabis risk permanently damaging their intelligence, attention span and memory, according to one of the biggest reports into the impact of the long term impact of the drug.

Researchers from King's College London and Duke University in the United States followed the development of over 1,000 people from birth to the age of 38 and found that cannabis has a different and more damaging effect on young brains that on those of adults.

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