Frequent marijuana use could have a significant negative effect on teens' brains.
Teenagers and young adults who smoke marijuana regularly could experience consequences such as cognitive decline, poor attention and memory, and decreased IQ, the American Psychological Association reported.
"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 on the rise; 6.5 percent of high school seniors reported smoking marijuana daily in a 2012 study. About 31 percent of people between the ages of 18 and 25 reported using marijuana within the past month.
Brain imaging studies have shown significant structural changes in the brains of adolescent marijuana users. Abnormalities in the brain's gray matter (which is associated with intelligence) were observed in 16 to 18-year old that had increased their marijuana use over the past year. These findings remained consistency after the researchers adjusted to factors such as " major medical conditions, prenatal drug exposure, developmental delays and learning disabilities." People who have become addicted to marijuana can lose an average of six IQ points by adulthood, according to a 2012 longitudinal study of 1,037 participants.
"When considering legalization, policymakers need to address ways to prevent easy access to marijuana and provide additional treatment funding for adolescent and young adult users," she said. She also recommended that legislators consider regulating levels of tetrahydrocannabinol, or THC, the major psychoactive chemical in marijuana, in order to reduce potential neurocognitive effects.
Some legalized strains of marijuana have higher levels of THC (which is responsible for marijuana's psychological effects) than others. Some studies have suggesting frequently smoking marijuana with high THC levels can lead to future problems with depression and anxiety.
"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." Current treatments for marijuana addiction among adolescents, such as brief school interventions and outpatient counseling, can be helpful but more research is needed to develop more effective strategies and interventions, he added.
