A study which appeared online in the Proceedings of the National Academy of Sciences criticized earlier findings that heavy cannabis use while young causes IQ to drop over time, reported Tracy Miller at the New York Daily News.
The study, performed by research economist Ole Rogeberg at the Ragnar Frisch Center for Economic Research in Norway, found that an earlier study, published in August 2012 by a team at Duke University, failed to take into consideration the effects of poverty on IQ scores.
“The question reminds me of something adults say when kids make weird faces: ‘Careful, or your face will stay that way,’ ” Rogeberg said. “It is certainly possible that in the long term, heavy cannabis use has a permanent effect or persistent effects on the brain. But to find out what these changes are and what they mean is not easy.
“We can’t just look at the short-term effects and assume that these gradually become fixed and permanent over time,” Rogeberg said.
Rogeberg’s team used computer modeling to show that the Duke University research failed to show a causal relationship between pot smoking and IQ. The Duke team had found that teenagers who used marijuana weekly and continued to smoke into adulthood lost an average of eight IQ points by the time they were 38, even if they stopped smoking weed during that time.
“Recent research indicates that IQ and brainpower are kind of like muscular strength: strengthened if it is regularly challenged,” Rogeberg said, reports Health Daily. “IQ is strengthened or sustained by taking education, studying hard, spending time with smart, challenging people, doing demanding work in our jobs.”
“Some kids, unfortunately, are burdened with a poor home environment, poor self-control and conduct problems,” Rogeberg said. “These kids are likely to gradually shift away from the kinds of activities and environments that would exercise their IQs.”
Meanwhile, the research team behind the earlier study huffily defended their flawed data.
“While Dr. Rogeberg’s ideas are interesting,” condescended Duke University researchers Terrie Moffitt, Avshalom Caspi and Madeline Meier in a statement, “they are not supported by our data.”