Addiction and substance use disorders are characterized by diminishing control over seeking a rewarding stimulus despite negative personal and interpersonal consequences. Eventually, the initial reward may no longer be experienced as pleasurable. This is usually accompanied by craving for the stimulus, needing a higher dose to maintain effects (ie, tolerance), and withdrawal symptoms on abstinence.

Addiction commonly involves a substance:

• Alcohol use disorder
• Benzodiazepine use disorder
• Cannabis use disorder
• Cocaine use disorder
• Methamphetamine use disorder
• Nicotine dependence (tobacco use disorder)
• Opioid use disorder
• Phencyclidine use disorder

Addiction can also involve an activity or behavior not related to substance use. Some common excessive behavior patterns include gambling, internet gaming, shopping, sex, eating, and exercise. With the exception of gambling, behavioral addiction disorders lack diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Some of these repetitive behaviors overlap with impulse disorders and obsessive-compulsive disorder (OCD), in which a person loses voluntary control over specific activities. It is thus important to consider these disorders in a differential diagnosis.

Disordered substance use is associated with increasing amounts of time spent in obtaining, taking, and recovering from the substance at the expense of time otherwise spent in other activities; unsuccessful efforts to decrease the substance use; and continuation despite recognizing its harmful effects. For many substances of abuse, genetic susceptibility is likely.

Studies support an increased association of addiction disorders among patients with comorbid schizophrenia, bipolar disorder, depression, and personality disorders (particularly antisocial and borderline personality disorders). The course is variable and dependent on many factors including the particular substance of abuse. Patients with comorbid psychiatric diagnoses ("dual diagnoses") often have more prolonged courses, perhaps due to inadequate diagnosis and treatment of the comorbidity.

Patients with these disorders may have an increased risk of various general medical conditions.