Regular marijuana use bad for teens' brains

http://www.eurekalert.org/pub_releases/2014-08/apa-rmu080414.php

PUBLIC RELEASE DATE: 9-Aug-2014

Contact: Audrey Hamilton
American Psychological Association
Regular marijuana use bad for teens' brains
Psychology and public health experts weigh in on potential effects of legalization on youth

WASHINGTON –- Frequent marijuana use can have a significant negative effect on the brains of teenagers and young adults, including cognitive decline, poor attention and memory, and decreased IQ, according to psychologists discussing public health implications of marijuana legalization at the American Psychological Association's 122nd Annual Convention.

"It needs to be emphasized that regular cannabis use, which we consider once a week, is not safe and may result in addiction and neurocognitive damage, especially in youth," said Krista Lisdahl, PhD, director of the brain imaging and neuropsychology lab at University of Wisconsin-Milwaukee.

Marijuana use is increasing, according to Lisdahl, who pointed to a 2012 study showing that 6.5 percent of high school seniors reported smoking marijuana daily, up from 2.4 percent in 1993. Additionally, 31 percent of young adults (ages 18 to 25) reported using marijuana in the last month. People who have become addicted to marijuana can lose an average of six IQ points by adulthood, according to Lisdahl, referring to a 2012 longitudinal study of 1,037 participants who were followed from birth to age 38.

Brain imaging studies of regular marijuana users have shown significant changes in their brain structure, particularly among adolescents, Lisdahl said. Abnormalities in the brain's gray matter, which is associated with intelligence, have been found in 16- to 19-year-olds who increased their marijuana use in the past year, she said. These findings remained even after researchers controlled for major medical conditions, prenatal drug exposure, developmental delays and learning disabilities, she added.

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