A ground breaking study out of New Zealand has found that regularly using marijuana at a young age and for prolonged periods of time will lower a person’s I.Q. by as much as eight points.
The research was published Monday in the Proceedings of the National Academy of Sciences.
The study is being described as “ground-breaking” because of its clear results and implications.
“I think this is the cleanest study I’ve ever read,” said Dr. Nora Volkow, director of the National Institute on Drug Abuse, which helped fund the research.
Analysts examined users before they started using marijuana and after they stopped, over a period of 25 years.
The study looked at 1, 000 people in the New Zealand town of Dunedin starting in 1973 and tested their I.Q. at the age of 13 and 38. They were tested on their focus, memory, reasoning and processing speed. They were also asked about their marijuana usage every five years, and close friends and family members were also asked about the memory and attention problems of the participants.
Researchers found there was a drop of eight I.Q. points between the age of 13 and 38, for those who had become dependent on marijuana by the age of 18. There was little to no drop in those who became dependent on the drug as adults. “Dependants” were those who used cannabis at least four days a week over the course of the study.
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Dr. Steven Laviolette of the University of Western Ontario’s School of Medicine and Dentistry says, “there is a neuro-developmental window of vulnerability during which exposure to cannabis leads to longer term effects on I.Q. expression in later adulthood.”
An eight point drop for a person of average intelligence means that individual now ranks in the bottom third of the population in terms of intelligence.
Quitting pot by age of 38 didn’t remove brain deficits for those who started young.
“During this adolescent period of brain development there is circuitry that is being formed and reformed,” says Laviolette. “When you expose the brain to certain chemicals during this period you can adversely modulate how these pathways are being formed.”
Experts say the results of marijuana can affect the user for the rest of their life.
“On average, IQ should be stable as a person ages,” said Madeline Meier of Duke University, lead researcher of the study.
“We know that IQ is a strong determinant of a person’s access to a college education, lifelong total income, their access to a job, their performance on a job,” she said. “Somebody who loses eight IQ points in their teens and twenties may be disadvantaged compared to their same age peers in most of the important aspects of life, and for years to come. Parents should understand that their adolescents are particularly vulnerable.”
The study comes at a time when more and more young people are using marijuana, possibly even more than cigarettes and do not think it is risky.
A Health Canada study, “The Canadian Alcohol and Drug Use Monitoring Survey of 2011,” said that cannabis use among Canadians was 9.1% and that the average age of first use was 15.9 years.
The U.S. Center for Disease Control and Prevention reported in June (2012) that 23 per cent of American high school students said they recently smoked marijuana while 18 per cent said they smoked cigarettes.
The United Nations World Drug Report of 2012 (June) says that up to 3.8 per cent of the world’s population has consumed cannabis recently and that it is largely a youth phenomenon that begins during the teenage years and peaks between the ages of 18 to 25, the key years of a young person’s brain development.
-with files from The Associated Press
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