Alcohol and Marijuana Use Creates Cognitive Deficits in Adolescents

Posted on October 25th, 2010
Posted in Teens

Heavy alcohol and marijuana use has historically been known to cause cognitive deficits in adults, but now more research over the past decade has been focusing on the adverse effects that adolescents experience from excessively using these substances.

The latest study by researchers at the University of New Mexico’s School of Medicine, available in the January 2011 issue of Alcoholism: Clinical & Experimental Research, has found that heavy alcohol and marijuana use by teenagers leads to brain impairment in the region that controls social skills, decision-making, and judgment. This area, located in the prefrontal lobe, is significantly damaged if teenagers excessively use alcohol and marijuana, as their young brains are still developing and have not completed their neurocognitive circuitry.

Lead researcher Robert Thoma, Ph.D. and his colleagues tested the neuropsychological performance of 48 adolescents who had different involvements with alcohol and marijuana use. One group, consisting of 15 healthy nonuser adolescents, served as the study’s control group; a second group consisted of 19 adolescents diagnosed with a substance abuse disorder or dependency; and a third group consisted of 14 adolescents who had a family history of alcohol use disorder (AUD) but whom did not have a substance abuse disorder themselves. All of the participants were between the ages of 12 and 18 years. The researchers measured such factors as age, how many drinks participants had per drinking day, percentage of drinking days, and percentage of days using marijuana. Then the researchers tested the participants on several neuropsychological measures including verbal reasoning, visuospatial ability, executive function, memory, attention, and processing speed.

Adolescents who demonstrated the highest percentages of drinking had the poorest performance abilities when it came to paying attention and executive functioning—as in responding appropriately to stimuli in their environments. Likewise, teenagers who showed more frequent use of marijuana demonstrated the poorest memory performance. These findings emulate other studies from the last decade that have found strong associations between marijuana use and memory problems, as well as binge drinking and disruptions to brain processes responsible for attention and planning skills.

Overall, those adolescents with substance abuse disorders were found to have the lowest scores on attention, memory, and processing speed measures. Interestingly, adolescents who did not use illicit substances but had a family history of AUD showed the lowest scores on visuospatial ability tests. The researchers note that these particular adolescents, although they did not show symptoms of fetal alcohol syndrome, may have been exposed to alcohol use in utero, which may have attributed to their spatial skill deficiencies. This finding was significant in the researchers’ analysis in order to help identify problems experienced specifically by teenagers who use alcohol, and problems experienced specifically by teenagers who were exposed to prenatal alcohol use. As it turns out, the two different exposures to alcohol use—although they both caused damage to neural cognition—did not produce the same deficiencies.

Based on these findings, the study’s researchers strongly urge the need for prevention strategies and treatment resources for adolescents who abuse substances. Because neurocognitive development is still occurring in their young brains, disruption of this process due to alcohol or marijuana use could seriously impose on their cognitive growth and brain function.

Reassuringly, similar studies on adults have indicated that brain function that has become damaged due to excessive drinking could partially be recovered after a period of abstinence. In line with these findings, Thoma and his team hope to conduct further investigation on the impact of cessation among adolescent binge drinkers to determine if abstinence helps their brains’ improve cognitive function since they are still undergoing brain growth. Prior research has established that reduction in alcohol consumption or abstinence among problem drinkers minimizes the level of brain impairment caused by alcohol.

Source: Alcoholism: Clinical and Experimental Research, Adolescent Substance Abuse: The Effects of Alcohol and Marijuana on Neuropsychological Performance, October 19, 2010


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