Drinking may harm adolescents' ability to concentrate and to understand spatial relationships. A recent study led by Susan Tapert at the University of California, San Diego compared the standardized test scores of 76 12 to 14 year old kids with their scores after about three years. At the three-year follow-up, 36 of the kids had begun drinking at moderate to heavy levels and 40 continued not using alcohol or other drugs. The study defined moderate to heavy drinking as drinking at least monthly and having three or more drinks at a time, or drinking less frequently, but having four or more drinks at a time. The kids in this study were consuming an average of about eight drinks per month by the time they reached the follow-up.

During the study's three-year time period, the team discovered once teens began to drink, they performed more poorly on cognitive tests than before they began drinking. Interestingly, the kinds of skills affected varied between girls and boys.

The researchers found that girls' scores on tasks requiring them to visualize and reproduce a complicated line drawing decreased after they began drinking. The researchers also found that boys' scores on tests requiring sustained attention decreased after they began drinking.

Tapert's study suggests that these behavioral effects may point toward alcohol's underlying effect on brain structure. Brain scans demonstrate that adolescent drinking can reduce the health of white matter in the brain. White matter is where brain cells communicate with each other, so damage to this area can result in slower, less efficient thinking. Reduced white matter integrity may cause girls to have difficulty understanding spatial relationships. This damage may be long-lasting since the adolescent brain is still undergoing significant developmental changes, making it especially vulnerable to alcohol's toxic effects.

Also see: Altered white matter integrity in adolescent binge drinkers, McQueeny T, Schweinsburg BC, Schweinsburg AD, Jacobus J, Bava S, Frank LR, & Tapert SF, Alcoholism: Clinical and Experimental Research, 2009, 33, 1278-1285.