The Grim Neurology of Teenage Drinking - New York Times

Nowadays, we know that pregnant women should not drink because it can harm their babies. But few of us realize that teenagers should not drink either for neurobiological reasons. Drinking alcohol injures the brain in teenagers and adults. But the developing brains of teenagers may be especially vulnerable to brain injury. Alcohol can impair their brain development and cause "long-term cognitive consequences" such as poor memory.

The good news is, quitting drinking may reverse the damage. "Adult alcoholics who stop drinking are known to recover cognitive function over time. The same may hold true for hard-drinking teenagers." However, part of the damage alcohol does is to areas of the brain involved in planning and impulse control, making teenagers who drink more susceptible to forming an addiction to alcohol. That's why drinking at an early age is a bad idea.