Experts once believed that it took a long period of heavy drinking to injure the brain, but mounting research suggests that alcohol may readily damage the developing brains of teenagers, the New York Times reported July 4.

Preliminary animal research has shown that doses of alcohol similar to binge drinking episodes may cause cellular damage to the forebrain and hippocampus of adolescents, perhaps explaining why -- as a different study of human subjects recently found  -- people who begin drinking at a young age are at much higher risk of becoming alcoholics. Studies also have shown that young drinkers perform poorly on a variety of cognitive tests.

Like this story? Get more by e-mail
Sign up for free daily or weekly updates

"There is no doubt about it now: there are long-term cognitive consequences to excessive drinking of alcohol in adolescence," said Aaron White, assistant research professor in the psychiatry department at Duke University. "We definitely didn't know 5 or 10 years ago that alcohol affected the teen brain differently. Now there's a sense of urgency. It's the same place we were in when everyone realized what a bad thing it was for pregnant women to drink alcohol."

Researchers have found that alcohol suppresses the action of chemical receptors in the hippocampus of young rats, impairing the development of new memories. Drinking affected the learning ability of young rats far more than it impaired the cognitive function of older rats. While it is uncertain how directly applicable the rat studies are to people, the findings are consistent with recent research exploring the neurobiological effects of alcohol in adolescent humans.

Young drinkers may experience more alcohol-related "blackouts" than previously believed, which may be explained by the effect of drinking on the developing hippocampus. Drinking also appears to make the brain less responsive to the neurotransmitter GABA among young people; GABA helps induce calmness and sleepiness, which may be why young drinkers can often remain conscious and keep drinking even after older drinkers pass out.

"Clearly, something is changed in the brain by early alcohol exposure," said Scott Swartzwelder, a neuropsychologist at Duke and at the Veterans Affairs Medical Center in Durham, N.C. "It's a double-edged sword and both of the edges are bad. Teenagers can drink far more than adults before they get sleepy enough to stop, but along the way they're impairing their cognitive functions much more powerfully."

Impulse control also is impaired by drinking, research shows -- a particular hazard for already impetuous youth. "Alcohol creates disruption in parts of the brain essential for self-control, motivation and goal setting," said University of North Carolina researcher Fulton Crews. "Early drinking is affecting a sensitive brain in a way that promotes the progression to addiction."

"Let's say you've been arrested for driving while drunk and spent seven days in jail," Crews added. "You'd think, 'No way am I going to speed and drive drunk again,' because you have the ability to weigh the consequences and the importance of a behavior. This is exactly what addicts don't do."