Although medical experts have been unable to conclusively determine what causes people to abuse drugs, there have been a number of explanations offered. People appear to use drugs for a variety of different reasons. Some may begin using drugs in adolescence because of peer pressure or beliefs that it makes them seem more sophisticated or grown up, while others might start using drugs as an expression of rebellion against the dictates of their parents or society in general. In recent years, there has been a great deal of research into the possibility of a biological influence. Proponents of this theory approach drug addiction as a disease, and point to evidence suggesting a genetic predisposition to drug abuse. Other theorists believe the behavior is learned solely from observing others, or that the use of drugs is somehow reinforced or encouraged by social relationships. In addition, a person's belief systems or expectations about drugs may play a role in drug abuse. For example, it's not unusual for users of LSD (L-S-D) to claim that the drug expands their minds or gives them new insights into life's mysteries. However, regardless of the reason for initial usage, it's important to keep in mind that people are more likely to continue using drugs if they believe it makes them feel better. For more information, consult a health care provider.