Adolescence is a time for adventure and experiment. Many teenagers try alcohol or drugs at least once. Most don't develop a problem. But not all children and adolescents escape the dangers as easily. Instead, they are at risk for developing serious problems as a result of their youthful experiments. These problems are called substance-use disorders. It's important to know that "recreational use," such as using a substance once or twice, is not a substance disorder. To qualify as a substance disorder, the effects of alcohol or drug use must have a serious, negative impact on a teenager's life. Research and surveys have yielded a great deal of information about children and adolescents and substance use. There is ample evidence that substance abuse disrupts the normal process of adolescent development. A variety of negative outcomes, including serious drug use later in life, school failure, and poor judgment are associated with substance disorders. Substance abuse is the strongest predictor of car accidents, homicides, suicide, HIV exposure, and other medical and mental health conditions. Teenagers who abuse substances often have other untreated disorders - depression, ADHD, or anxiety - that increase their vulnerability. What can be done to forestall these problems? Early drug education, open communication, positive role models, and early recognition make a good start.