Addictive substances are chemicals or materials that can create physical and/or psychological dependencies. The U.S. government classifies these substances according to their potential for addiction and medical uses. Certain of them are strictly illegal to use, but others can be used under medical supervision. Some addictive substances that can be legally sold over-the-counter are caffeine, nicotine, alcohol, inhalants, cough medications, and certain psychotropic herbs. Common substances with medical uses that are illegal to use without a doctor’s prescription include cocaine, narcotic painkillers such as hydrocodone and oxycodone, barbiturates and benzodiazepines. Heroin and certain hallucinogens have no medical uses and are illegal to use at all. Marijuana is currently classified this way by the federal government, although some states have legalized marijuana for medical use and four states have now also legalized it for recreational use.
A person using an “addictive substance” can develop what doctors call “substance abuse disorder” or “substance dependency.” The difference between the two disorders is that those “dependent” on substances go through physical withdrawal syndromes when they quit. Even if they do not have to undergo physical withdrawal syndromes, people can find it hard to overcome psychological dependencies on substances. For example, ketamine and LSD are drugs that do not produce physical withdrawal symptoms when you quit using them. However, people can become so involved in a lifestyle that involves clubbing and using hallucinogens or so overly fascinated by altered states of consciousness that it becomes difficult for them to quit without professional help.