Pleasure rewards eating, drinking, and sex but people have isolated pleasure from those activities with psychoactive drugs. Drug use can result in substance use disorder (addiction) characterized by craving, using compulsively with a disregard for negative health and social consequences. Prolonged used leads to drug tolerance and unpleasant withdrawal symptoms. While initially drug use is positively reinforcing, continued use is motivated by the relief of drug withdrawal symptoms. Becoming addicted depends on a person's genetic disposition for addiction combined with an environment conducive for drug use. Stress and environmental triggers induce craving and subsequent drug use. In the brain, psychoactive drugs act on dopamine and endorphins to activate neurons in the pleasure network. Excessive gambling, Internet gaming, Internet use, and exercise resemble substance abuse disorder (addiction).