OTTAWA, April 1 (UPI) -- Regular, heavy marijuana use can lead to drop in IQ points, but the effects appear to wear off after several consecutive months of not using the drug, according to a new study released Monday.
Psychologist Peter Fried and colleagues at Carleton University in Ottawa have tracked the development of 70 individuals since birth. Intelligence quotient or IQ scores were assessed when the study participants were 9 to 12 years old, before any of them had experimented with marijuana use. Those IQ scores were compared several years later to their scores when the participants reached 17 to 20 years old.
Study results showed those classified as heavy users, meaning they smoked more than five marijuana joints per week, experienced an average drop of 4.1 IQ points. However, IQ points were gained among the rest of the group, including light users, former users and non-users.
Researchers also pointed out that while heavy users did experience IQ declines, their overall scores still were above the average IQ level. Had participants not been tested prior to marijuana use during their preteen years, researchers said, they would have appeared to have normal cognitive function.
"Three months after being clean, they had recovered" to their previous IQ levels, Fried told United Press International. "I don't want to suggest by being clean, all cognitive effects disappear."
More study is needed, he said, to better understand what, if any, lingering effects marijuana use might have on the brain.
The findings are published in the April issue of Canadian Medical Association Journal.
Fried said while there is debate whether marijuana can be physicially addictive, evidence indicates it certainly can be psychologically addictive. Research shows, Fried said, that marijuana serves as a psychological crutch for many people to ease anxiety and depression.
"There's some nice things about marijuana, there's no question about. The high is nice, otherwise this wouldn't be an issue," Fried said.
Although Fried said the law against marijuana needs to be revamped in Canada, he is unsure how, since it is unclear what, if any, the longer term effects of the drug may be on a user's mind, particularly when it comes to decision making. The effects of marijuana use during pregnancy also are not clear.
What makes marijuana unique is that people can test positive for it even long after they have stopped using it, said Patricia Reggio, a professor of chemistry and biochemistry at Kennesaw State University in Kennesaw, Ga.
Marijuana is not water soluble so it is not easily excreted from the body and it gravitates to fat tissue so that it takes a while to clear out.
"It really has a long residence time in the body," Reggio told UPI. How long it will take to process marijuana out of the body depends on the individual's metabolism, she added.
There are cannabinoid or marijuana receptors in the part of the brain associated with memory, Reggio added. "So people that use marijuana regularly, will probably wind up having some short-term memory loss," she said.
But even after the high wears off, marijuana is still leaving an impact. "As long as somebody's got some cannabinoids somewhere in the their system," Reggio said, "they're likely to have some memory effects."
(Reported by Katrina Woznicki in Washington)
