One unfavorable or unintended response of medical treatment is addiction to a prescription drug. A number of drugs used as medicines can lead to addiction or abuse in some people. These drugs include opioids, antihistamines, and steroids, among others. The most commonly abused prescription drugs are those used to treat psychological problems. Barbiturates and amphetamines have the highest potential for abuse. Others, such as the antipsychotics, antidepressants, and lithium salts, have a lower abuse potential.

According to the National Household Survey on Drug Abuse, 3.8 million people ages 12 and older were using prescription drugs for nonmedical reasons in 2000. This represents 1.7 percent of the population aged 12 and older, about the same rate as in 1999 (1.8%). Nonmedical use of prescription drugs increased among youths aged 16 and 17 between 1999 and 2000, from 3.4 percent to 4.3 percent. Adolescent girls were somewhat more likely to use prescription drugs nonmedically than boys (3.3% compared to 2.7%). Amphetamines...