Adolescence is a time of many changes—physical, mental, social, and emotional. Most adolescents adapt to these changes in healthy ways. Others experience turmoil and conflict. They become deeply unsettled and confused as they attempt to cope with this time in their lives. This unhappiness and confusion may lead them toward dangerous or deviant behavior, such as drug use. A single episode of drug use does not necessarily lead to further use, but several episodes may lead to ever-increasing use, resulting in abuse and dependence. Continued drug use can have serious consequences, not only during adolescence but into adulthood as well.

Whether a young person continues to use a drug depends on three major factors: age of first use, type of drug used, and reasons for use. Younger adolescents who try one type of drug may go on to sample...