Study questions link between teen pot smoking and IQ decline

NEW YORK -- A new analysis is challenging the idea that smoking marijuana during adolescence can lead to declines in intelligence.

See Full Article

Instead, the new study says, pot smoking may be merely a symptom of something else that's really responsible for a brainpower effect seen in some previous research.

It's not clear what that other factor is, said Joshua Isen, an author of the analysis. But an adolescent at risk for smoking pot "is probably going to show this IQ drop regardless of whether he or she is actually smoking marijuana," said Isen, a lecturer in psychology at Loyola Marymount University in Los Angeles.

The study was released Monday by the Proceedings of the National Academy of Sciences. Some prior research has led to suggestions that the developing adolescent brain is particularly vulnerable to harm from marijuana.

Studying the topic is difficult because children can't ethically be randomly chosen to either take illicit drugs or abstain for years so that their outcomes can be compared. Scientists have to assess what people do on their own.

For the new work, the researchers examined data that had been collected for two big U.S. studies of twins. They focused on 3,066 participants who were given a battery of intelligence tests at ages 9 to 12 -- before any of them had used marijuana -- and again at ages 17 to 20.

They tracked changes in the test scores and studied whether those trajectories were worse for marijuana users than for non-users. Most tests revealed no difference between the two groups, but users did fare more poorly than abstainers in tests of vocabulary and general knowledge.

If smoking pot harmed test scores, the researchers reasoned, people who'd smoked more pot should show poorer trends than those who'd smoked less. But that's not what the data revealed. Among users, those who'd smoked more than 30 times or used it daily for more than a six-month stretch didn't do worse.

The study also looked at 290 pairs of twins in which one had used marijuana and the other had not. The members of each pair had grown up together and 137 sets were identical twins so they shared the same DNA. Again, the pot users did not fare worse than their abstaining twin siblings.

So, the researchers concluded, pot smoking itself does not appear responsible for declines in test scores. Isen noted, however, that the work says nothing about other potential harmful consequences of smoking marijuana in adolescence.

Dr. Nora Volkow, director of the National Institute on Drug Abuse, said that while the study has some limitations, it is important and deserves to be followed up with more research. She noted the government has already launched a project to follow about 10,000 children over time to assess the impact of marijuana and other drug use.

A prominent 2012 study had indicated long-term IQ harm from pot smoking in teenagers. An author of that research said the new work does not conflict with her finding. Terrie Moffitt of Duke University said her study dealt with marijuana use that was far more serious and longer-lasting than the levels reported in the new work.



Advertisements

Latest Tech & Science News

  • Google's next version of Android will be called 'Oreo'

    Tech & Science CBC News
    An upcoming update to Google's Android software finally has a delectable name. The next version will be known as Oreo, extending Google's tradition of naming each version after a sweet treat. L’ready or not, you’ve made it to the sweet treat hall of fame. Source
  • Victoria tech company hopes to entice new talent with five-hour work days

    Tech & Science CTV News
    A Victoria technology company has switched to five-hour work days in an effort to attract new employees. A boom in the tech industry has meant that companies have had to offer more than a unique workplace and cutting edge perks to draw in potential new talent. Source
  • Iran says Twitter ready to talk on unblocking site: report

    Tech & Science CTV News
    TEHRAN, Iran -- Iran's new telecommunications minister says Twitter is ready to talk about unblocking access to the microblogging site. The state-owned IRAN newspaper quoted Mohammad Javad Azari Jahromi on Tuesday as saying Twitter has "officially announced readiness to talk with Iran for resolving the problems. Source
  • Rain, clouds don't dampen eclipse excitement in Missouri

    Tech & Science CBC News
    People from all over the world converged Monday on St. Joseph, Mo., a town nestled along the Missouri River just north of Kansas City, to watch an event that many said comes once in a lifetime: a total solar eclipse. Source
  • Warm ocean takes toll on kelp forest

    Tech & Science CTV News
    APPLEDORE ISLAND, Maine - When diving in the Gulf of Maine a few years back, Jennifer Dijkstra expected to be swimming through a flowing kelp forest that had long served as a nursery and food for juvenile fish and lobster. Source
  • Warm oceans take toll on kelp forest

    Tech & Science CTV News
    APPLEDORE ISLAND, Maine - When diving in the Gulf of Maine a few years back, Jennifer Dijkstra expected to be swimming through a flowing kelp forest that had long served as a nursery and food for juvenile fish and lobster. Source
  • Vanishing kelp: Warm ocean takes toll on undersea forests

    Tech & Science CTV News
    APPLEDORE ISLAND, Maine -- When diving in the Gulf of Maine a few years back, Jennifer Dijkstra expected to be swimming through a flowing kelp forest that had long served as a nursery and food for juvenile fish and lobster. Source
  • Brazen bear punched after breaking into home on B.C.'s Sunshine Coast

    Tech & Science CBC News
    Police say a black bear has been put down after it broke into a home and terrified a family in Gibsons, B.C. Sunshine Coast RCMP say Eleri Froude was home with her two sons and a family friend on Saturday evening when an adult male bear wandered in through the sliding glass door. Source
  • Eclipse science: From galloping giraffes to solar wisps

    Tech & Science CTV News
    NASHVILLE -- The giraffes ran in circles. The flamingos huddled together. And the rhinos just looked confused. At the Nashville Zoo, visitors watched and recorded how the animals behaved when the sky turned dark during Monday's total solar eclipse. Source
  • Grizzly-human conflict in southwestern Alberta rising: study

    Tech & Science CTV News
    EDMONTON -- Scientists say conflict between grizzly bears and people in southwestern Alberta is growing. University of Alberta researchers combed through 15 years worth of data on contact between humans, black bears, grizzlies, wolves and cougars in the province's southern foothills, mountains and plains. Source