Drugs have been cultivated around the world. Drug use is unique to modern Western cultures. Drug addiction is caused by physical dependence. Withdrawal symptoms and tolerance are the result of compensatory mechanisms. The withdrawal symptoms that occur in heroin addicts are less dangerous than those that occur in alcoholics.
Withdrawal symptoms are primarily the opposite of the effects of the drug itself.
The most appropriate definition of drug addiction would emphasize negative personal, legal, and social effects of drug taking. Drugs that do not produce physical dependence can still be addictive. A reinforcing stimulus is most effective if it occurs immediately after the behavior. Positive reinforcement works better in humans than in laboratory animals. Immediacy of reinforcement takes precedence over quantity.