Substance use disorder

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 (SID) 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.

In the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (2013), also known as DSM-5, the DSM-IV diagnoses of substance abuse and substance dependence were merged into the category of substance use disorders. The severity of substance use disorders can vary widely; in the DSM-5 diagnosis of a SUD, the severity of an individual's SUD is qualified as mild, moderate, or severe on the basis of how many of the 11 diagnostic criteria are met. The International Classification of Diseases 11th revision (ICD-11) divides substance use disorders into two categories: (1) harmful pattern of substance use; and (2) substance dependence.

In 2017, globally 271 million people (5.5% of adults) were estimated to have used one or more illicit drugs. 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. 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.

Substance use disorders (SUDs) are highly prevalent and exact a large toll on individuals' health, well-being, and social functioning. Long-lasting changes in brain networks involved in reward, executive function, stress reactivity, mood, and self-awareness underlie the intense drive to consume substances and the inability to control this urge in a person who suffers from addiction (moderate or severe SUD). Biological (including genetics and developmental life stages) and social (including adverse childhood experiences) determinants of health are recognized factors that contribute to vulnerability to or resilience against developing a SUD. Consequently, prevention strategies that target social risk factors can improve outcomes and, when deployed in childhood and adolescence, can decrease the risk for these disorders.

This section divides substance use disorder causes into categories consistent with the biopsychosocial model. However, it is important to bear in mind that these categories are used by scientists partly for convenience; the categories often overlap (for example, adolescents and adults whose parents had—or have—an alcohol use disorder display higher rates of alcohol problems, a phenomenon that can be due to genetic, observational learning, socioeconomic, and other causal factors); and these categories are not the only ways to classify substance use disorder etiology.

Similarly, most researchers in this and related areas (such as the etiology of psychopathology generally), emphasize that various causal factors interact and influence each other in complex and multifaceted ways.

Among older adults, being divorced, separated, or single; having more financial resources; lack of religious affiliation; bereavement; involuntary retirement; and homelessness are all associated with alcohol problems, including alcohol use disorder. Many times, issues may be interconnected, people without jobs are most likely to abuse substances which then makes them unable to work. Not having a job leads to stress and sometimes depression which in turn can cause an individual to increase substance use. This leads to a cycle of substance abuse and unemployment. The likelihood of substance abuse can increase during childhood. Through a study conducted in 2021 about the effect childhood experiences have on future substance use, researchers found that there is a direct connection between the two factors. Individuals that had experiences in their childhood which left them traumatized in some way had a much higher chance of substance abuse.