This document summarizes research on why teens drink alcohol and the effects of alcohol consumption. It finds that teens primarily drink alcohol to have fun or celebrate, but are also influenced by parents, peers and media portrayals. Alcohol advertising spends billions promoting alcohol usage. Underage drinking is common in the US, with the average teen starting at age 13. The document outlines how factors like body size, gender, food and medications can influence alcohol's effects on the brain and body. Excessive drinking can impair judgment and coordination and potentially cause injury or death.