Teens Smoking Pot Have Less IQ

Marijuana is on the most commonly used illicit drug in the United States. Most of the Marijuana users blind themselves to the thought that smoking pot has no negative effect on their health. But the recent study by a team of international researchers is an eye opener for the all the teenagers in the marijuana trap before the age of 18.

The study carried in the Proceedings of the National Academy of Sciences claims that continuous use of marijuana (more than once a week) before 18 resulted in drop of IQ points.

The study that was lead by Madeline Meier, a post-doctoral researcher at Duke University followed more than 1000 New Zealanders, individuals using cannabis in adolescence and hooked to it for years afterwards showed an average decline in IQ of 8 points.

The sad part if that quitting pot does not seem to reverse the loss. The important factor in this study is the age of onset for marijuana and the development of the brain as those who never tried marijuana till they were adults did not show any mental decline.

"Before age 18, however, the brain is still being organized and remodeled to become more efficient, she said, and may be more vulnerable to damage from drugs. Marijuana is not harmless, particularly for adolescents," said Meier, who produced this finding from the long term Dunedin Multidisciplinary Health and Development Study. 

On monitoring the 1037 children born in 1972-73 in Dunedin, New Zealand from birth to age 38, they learnt that the subjects who were addicted to pot as teens scored worse on most of the tests. And at the age of 38 they were given tests to assess memory, processing speed, reasoning and visual processing.

On interviewing friends and relatives of the cannabis users, they learn that the subjects have attention and memory problems.

Terrie Moffitt a psychologist who holds dual appointments at Duke and the Institute of Psychiatry at King's College London said, "The decline in IQ among persistent cannabis users could not be explained by alcohol or other drug use or by having less education."

While 8 IQ points may not sound like a lot on a scale where 100 is the mean, a loss from an IQ of 100 to 92 represents a drop from being in the 50th percentile to being in the 29th, Meier said. Higher IQ correlates with higher education and income, better health and a longer life, she said. "Somebody who loses 8 IQ points as an adolescent may be disadvantaged compared to their same-age peers for years to come," Meier said.

Laurence Steinberg, a Temple University psychologist who was not involved in the research said, "This study is among the first to distinguish between cognitive problems the person might have had before taking up marijuana, and those that were apparently caused by the drug. This is consistent with what has been found in animal studies. But it has been difficult to measure in humans."

 "This study points to adolescence as a time of heightened vulnerability," Steinberg said. "The findings are pretty clear that it is not simply chronic use that causes deficits, but chronic use with adolescent onset."

Meier concluded saying, "What isn't possible to know from this study is what a safer age for persistent use might be, or what dosage level causes the damage. After many years of decline among US teens, daily marijuana use has been seen to increase slightly in the last few years.  Last year, for the first time, US teens were more likely to be smoking pot than tobacco."