Substance use disorder (SUD) is the persistent use of drugs despite substantial harm and adverse consequences to self and others. Related terms include substance use problems and problematic drug or alcohol use. Along with substance-induced disorders (SIDs) they are encompassed in the category substance-related disorders.
Substance use disorders vary with regard to the average age of onset. It is not uncommon for those who have SUD to also have other mental health disorders. Substance use disorders are characterized by an array of mental, emotional, physical, and behavioral problems such as chronic guilt; an inability to reduce or stop consuming the substance(s) despite repeated attempts; operating vehicles while intoxicated; and physiological withdrawal symptoms. Drug classes that are commonly involved in SUD include: alcohol (alcoholism); cannabis; opioids; stimulants such as nicotine (including tobacco), cocaine and amphetamines; benzodiazepines; barbiturates; and other substances.