Drug abuse refers to the habitual use of drugs not needed for therapeutic purposes to alter mood or consciousness. Continued drug use can lead to physical and mental dependence. Commonly abused drugs include marijuana, cocaine, heroin, and alcohol. Signs of drug abuse include changes in appearance, behavior, and physical or psychological symptoms. Prevention of drug abuse requires education to reduce demand as well as law enforcement to reduce the supply of illicit drugs. Treatment options include behavioral therapies, hospitalization, and helping addicts change their social environment.