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Overview of Substance-Related Disorders


Mashal Khan

, MD, NewYork-Presbyterian Hospital

Reviewed/Revised Oct 2022
Topic Resources

Medications and other substances, whether used for legitimate medical purposes, as a habit (for example, caffeine), or recreationally, are an integral part of everyday life for many people (see table Drugs with Both Medical and Recreational Uses Drugs With Medical and Recreational Uses Drugs With Medical and Recreational Uses ).

Substance misuse and other substance-related disorders can arise when drugs that directly activate the brain's reward system are taken for the feelings of pleasure they induce. The pleasurable sensations vary with the drug. The drugs are divided into 10 different classes based on the different effects they produce in the body:

Substance-related disorders can develop whether or not a drug is legal, is socially acceptable, or has an accepted medical use (with or without a prescription). Details about specific drugs and their effects are discussed elsewhere in THE MANUAL.

In discussions about controlled substances and drug use, the term "narcotics" is often used. This term refers to drugs that cause loss of feeling, a sense of numbness, and drowsiness, specifically opioids Opioids Opioids, a class of drugs derived from the opium poppy (including synthetic variations), are pain relievers with a high potential for misuse. Opioids are used to relieve pain, but they also... read more (drugs that bind to opiate receptors on cells). However, the term "narcotics" is also used in a broader (and inaccurate) sense to include any drug that is illegal or used illegitimately.


Substance use disorders generally involve behavior patterns in which people continue to use a substance despite having problems caused by its use. There may also be physiologic manifestations, including changes in brain circuitry. The common terms "addiction," "abuse," and "dependence" are too loosely and variably defined to be very useful in systematic diagnosis; "substance use disorder" is more comprehensive and has fewer negative connotations.

Drugs in the 10 classes vary in how likely they are to cause a substance use disorder. The likelihood is termed addiction liability and depends upon a combination of factors including

Scheduled Drugs

The Comprehensive Drug Abuse Prevention and Control Act (Controlled Substances Act) was implemented in the United States in 1970 and modified over the years to regulate the manufacture and distribution of certain classes of drugs, or controlled substances (see table Some Examples of Controlled Substances Some Examples of Controlled Substances* Some Examples of Controlled Substances* ).

Controlled substances are divided into 5 schedules (or classes) based on their potential for abuse, how accepted they are for medical use, and how safe they are when used under medical supervision. Schedule I drugs are considered the most harmful and therefore have the tightest controls. Schedule V drugs are considered the least harmful and are widely available. State and federal schedules may differ (see also US Drug Enforcement Administration Drug Schedules).


More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

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