Frequent Marijuana Use can Lower IQ, Cause Memory Problems in Teens

Frequent marijuana use can lead to cognitive decline, poor attention and memory problems in teenagers and young adults, researchers say.

The researchers were discussing the effects of marijuana legalization at the American Psychological Association's 122nd Annual Convention. They said that cannabis isn't a safe drug and can cause several problems in teens.

Marijuana is an easily accessible drug. About 48 percent of all people in the U.S. have used the drug at some point in their lives. According to recent estimates from the Centers for Disease Control and Prevention, more teens are smoking marijuana than cigarettes. Most teens and young adults believe that marijuana is a safe drug.

"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 the University of Wisconsin-Milwaukee, according to a news release.

Lisdahl said that previous research on teens' brain scan images has shown that marijuana causes structural changes in brains. Teens and young adults who increase frequency of smoking pot have abnormalities in the brain's grey volume.

Policymakers should consider regulating levels of tetrahydrocannabinol or THC to avoid the potential misuse of the drug. THC is the main, psychoactive ingredient in marijuana, Lisdahl suggests.

According to Alan Budney, PhD, of Dartmouth College, some strains of legalized marijuana have higher levels of THC. Depression, anxiety and psychosis are common problems faced by people who use highly potent THC.

"Recent studies suggest that this relationship between marijuana and mental illness may be moderated by how often marijuana is used and potency of the substance," Budney said. "Unfortunately, much of what we know from earlier research is based on smoking marijuana with much lower doses of THC than are commonly used today."