Drug abuse has a wide range of definitions related to taking a psychoactive drug or performance enhancing drug for a non-therapeutic or non-medical effect. All of these definitions imply a negative judgement of the drug use in question (compare with the term responsible drug use for alternative views). Some of the drugs most often associated with this term include alcohol, amphetamines, barbiturates, benzodiazepines, cocaine, methaqualone, and opium alkaloids. Use of these drugs may lead to criminal penalty in addition to possible physical, social, and psychological harm, both strongly depending on local jurisdiction.(2002). Mosby's Medical, Nursing, & Allied Health Dictionary. Sixth Edition. Drug abuse definition, p. 552. Nursing diagnoses, p. 2109. ISBN 0-323-01430-5. Other definitions of drug abuse fall into four main categories: public health definitions, mass communication and vernacular usage, medical definitions, and political and criminal justice definitions.

An estimated 4.7% of the global population aged 15 to 64, or 185 million people, consume illicit drugs annually.

Public health definitions

The Health Officers Council of British Columbia — in their 2005 policy discussion paper, A Public Health Approach to Drug Control in Canada — has adopted a public health model of psychoactive substance use that challenges the simplistic black-and-white construction of the binary (or complementary) antonyms "use" vs. "abuse". This model explicitly recognizes a spectrum of use, ranging from beneficial use to chronic dependence (see diagram to the right).

Medical definitions

In the modern medical profession, the two most used diagnostic tools in the world, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) and the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD), no longer recognise 'drug abuse' as a current medical diagnosis. Instead, they have adopted substance abuse as a blanket term to include drug abuse and other things.Physical dependence, abuse of, and withdrawal from drugs and other miscellaneous substances is outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) ). It's section Substance dependence begin with:

"Substance dependence When an individual persists in use of alcohol or other drugs despite problems related to use of the substance, substance dependence may be diagnosed. Compulsive and repetitive use may result in tolerance to the effect of the drug and withdrawal symptoms when use is reduced or stopped. This, along with Substance Abuse are considered Substance Use Disorders...."