Substance-related addiction, or substance related disorder is a disorder of intoxication, dependence, abuse, and substance withdrawal caused by various substances, both legal and illegal. These substances include: alcohol, amphetamines , caffeine, inhalants, nicotine, prescription medications that may be abused (such as sedatives), opioids (morphine, heroin), marijuana (cannabis), cocaine, hallucinogens, and phencyclidine (PCP).