The related concept of drug addiction has many different definitions. Some writers give drug addiction to the same meaning as substance dependence, others for example provide drug addiction a narrower meaning which excludes drugs without evidence of tolerance or withdrawal symptoms.

The American Society of Addiction Medicine has this definition for Addiction^{[citation needed]}: Addiction is a primary, chronic disease of brain reward, motivation, memory and related circuitry. Dysfunction in these circuits leads to characteristic biological, psychological, social and spiritual manifestations. This is reflected in the individual pursuing reward and/or relief by substance use and other behaviors. The addiction is characterized by impairment in behavioral control, craving, inability to consistently abstain, and diminished recognition of significant problems with one’s behaviors and interpersonal relationships. Like other chronic diseases, addiction involves cycles of relapse and remission. Without treatment or engagement in recovery activities, addiction is progressive and can result in disability or premature death.

Substance dependence

According to the current Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), substance dependence is defined as:

“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….” ^[6]

Substance dependence can be diagnosed with physiological dependence, evidence of tolerance or withdrawal, or without physiological dependence.

DSM-IV substance dependencies:

• 303.90 Alcohol dependence
• 304.00 Opioid dependence
• 304.10 Sedative, hypnotic, or anxiolytic dependence (including benzodiazepine dependence and barbiturate dependence)
• 304.20 Cocaine dependence
• 304.30 Cannabis dependence
• 304.40 Amphetamine dependence (or amphetamine-like)
• 304.50 Hallucinogen dependence
• 304.60 Inhalant dependence
• 304.80 Polysubstance dependence
• 304.90 Phencyclidine (or phencyclidine-like) dependence
• 304.90 Other (or unknown) substance dependence
• 305.10 Nicotine dependence