Substance use disorders

This page is reference information compiled from the cited sources. It is not medical advice. For any decision about health, diagnosis or care, consult a qualified professional.

What it is

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 categorized as substance-related disorders. Substance use disorders are characterized by an array of mental, emotional, physical, and behavioral problems. In the DSM-5, the DSM-IV diagnoses of substance abuse and substance dependence were merged into the category of substance use disorders. The ICD-11 divides substance use disorders into two categories: harmful pattern of substance use and substance dependence.

Key facts

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, a coexistence referred to as co-occurring disorders. In 2017, globally 271 million people were estimated to have used one or more illicit drugs, and of these, 35 million had a substance use disorder. An additional 237 million men and 46 million women have alcohol use disorder as of 2016. In 2017, substance use disorders from illicit substances directly resulted in 585,000 deaths, and direct deaths from drug use, other than alcohol, have increased over 60 percent from 2000 to 2015. Alcohol use resulted in an additional 3 million deaths in 2016. The severity of a substance use disorder in the DSM-5 is qualified as mild, moderate, or severe based on how many of the 11 diagnostic criteria are met.

When to seek professional help

The source associates professional care with situations involving an inability to reduce or stop consuming the substance despite repeated attempts. Professional help is indicated when substance use leads to operating vehicles while intoxicated or when physiological withdrawal symptoms are present. The source links professional care to the presence of other mental health disorders alongside a substance use disorder, known as co-occurring disorders. Seeking professional support is associated with a range of emotional and psychological problems including anger, guilt, depression, anxiety, and violence that affect the individual and their family. The source notes that housing instability and homelessness can create barriers to accessing treatment and recovery support, implying a need for professional intervention in those contexts.

Source: Substance use disorder (CC BY-SA 4.0 (Wikipedia)), retrieved 2026-09-19.