In the '50s and '60s, amphetamines were often prescribed for people who were depressed or overweight, and encouraged as a productivity enhancer. Beginning in the '70s, critics of the pharmaceutical industry and of the prescribing practices of doctors brought about severe restrictions on the medical use of amphetamines. As a result, the black market for these drugs grew, a change that promoted more abuse. Like other forms of amphetamine and cocaine, methamphetamine can be associated with a stubborn kind of drug dependence that leads to personality changes and physical exhaustion. The risk to a user depends a lot on the method by which the drug is consumed.
Many people inject or snort crystal meth.
People who inject methamphetamine may fall into the pattern of staying up on the drug for several days, then crashing into a stupor. In a short time they become emaciated and generally unhealthy. Some people do find amphetamines useful for specific purposes and take them only once in a while by mouth. Examples might include long-distance truck drivers, athletes before a big game, or dancers before a specific performance. If they rest afterward, this kind of amphetamine use isn't usually a problem.