Substance use disorder (SUD) is the persistent use of drugs despite the substantial harm and adverse consequences to one's own self and others, as a result of their use.[7][8] In perspective, the effects of the wrong use of substances that are capable of causing harm to the user or others, have been extensively described in different studies using a variety of terms such as substance use problems,[9] problematic drugs or alcohol use,[10][11] and substance use disorder.[12][13] The National Institute of Mental Health (NIMH) states that "Substance use disorder (SUD) is a treatable mental disorder that affects a person's brain and behavior, leading to their inability to control their use of substances like legal or illegal drugs, alcohol, or medications. Symptoms can be moderate to severe, with addiction being the most severe form of SUD".[14] Substance use disorders (SUD) are considered to be a serious mental illness that fluctuates with the age that symptoms first start appearing in an individual, the time during which it exists and the type of substance that is used.[15] 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.[7] 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.[7][16]
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.[17][18] 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.[19]
In 2017, globally 271 million people (5.5% of adults) were estimated to have used one or more illicit drugs.[20] Of these, 35 million had a substance use disorder.[20] An additional 237 million men and 46 million women have alcohol use disorder as of 2016.[21] In 2017, substance use disorders from illicit substances directly resulted in 585,000 deaths.[20] Direct deaths from drug use, other than alcohol, have increased over 60 percent from 2000 to 2015.[22] Alcohol use resulted in an additional 3 million deaths in 2016.[21]
Causes
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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 for 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.[23]
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.[24][25][26][27][28]
Social determinants
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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.[29] 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.[30] 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.[31]
Psychological determinants
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Psychological causal factors include cognitive, affective, and developmental determinants, among others. For example, individuals who begin using alcohol or other drugs in their teens are more likely to have a substance use disorder as adults.[2] Other common risk factors are being male, being under 25, having other mental health problems (with the latter two being related to symptomatic relapse, impaired clinical and psychosocial adjustment, reduced medication adherence, and lower response to treatment[32]), and lack of familial support and supervision.[2] (As mentioned above, some of these causal factors can also be categorized as social or biological). Other psychological risk factors include high impulsivity, sensation seeking, neuroticism and openness to experience in combination with low conscientiousness.[33][34]
Biological determinants
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Children born to parents with SUDs have roughly a two-fold increased risk in developing a SUD compared to children born to parents without any SUDs.[2] Other factors such as substance use during pregnancy, or the persistent inhalation of secondhand smoke can also influence a person's substance use behaviors in the future.[30]
Diagnosis
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Individuals whose drug or alcohol use cause significant impairment or distress may have a substance use disorder (SUD).[7] Diagnosis usually involves an in-depth examination, typically by psychiatrist, psychologist, or drug and alcohol counselor.[38] The most commonly used guidelines are published in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).[38] There are 11 diagnostic criteria which can be broadly categorized into issues arising from substance use related to loss of control, strain to one's interpersonal life, hazardous use, and pharmacologic effects.[7]
There are additional qualifiers and exceptions outlined in the DSM. For instance, if an individual is taking opiates as prescribed, they may experience physiologic effects of tolerance and withdrawal, but this would not cause an individual to meet criteria for a SUD without additional symptoms also being present.[7] A physician trained to evaluate and treat substance use disorders will take these nuances into account during a diagnostic evaluation.
Signs and symptoms
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Symptoms for a substance use disorder include behavioral, physical and social changes. Changes in behavior include being absent from school or work; changes in appetite or sleep patterns; personality and attitude changes; mood swings, and anxiety. Signs include physical changes such as weight gain or loss; tremors, and bloodshot eyes.[39] Different substances used can give different signs and symptoms.[40]
Severity
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Substance use disorders can range widely in severity, and there are numerous methods to monitor and qualify the severity of an individual's SUD. The DSM-5 includes specifiers for severity of a SUD.[7] Individuals who meet only two or three criteria are often deemed to have mild SUD.[7] Substance users who meet four or five criteria may have their SUD described as moderate, and persons meeting six or more criteria as severe.[7] In the DSM-5, the term drug addiction is synonymous with severe substance use disorder.[37][41] The quantity of criteria met offer a rough gauge on the severity of illness, but licensed professionals will also take into account a more holistic view when assessing severity which includes specific consequences and behavioral patterns related to an individual's substance use.[7] They will also typically follow frequency of use over time, and assess for substance-specific consequences, such as the occurrence of blackouts, or arrests for driving under the influence of alcohol, when evaluating someone for an alcohol use disorder.[7] There are additional qualifiers for stages of remission that are based on the amount of time an individual with a diagnosis of a SUD has not met any of the 11 criteria except craving.[7] Some medical systems refer to an Addiction Severity Index to assess the severity of problems related to substance use.[42] The index assesses potential problems in seven categories: medical, employment/support, alcohol, other drug use, legal, family/social, and psychiatric.[43]
Screening tools
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There are several different screening tools that have been validated for use with adolescents, such as the CRAFFT, and with adults, such as CAGE, AUDIT and DALI.[44] Laboratory tests to detect alcohol and other drugs in urine and blood may be useful during the assessment process to confirm a diagnosis, to establish a baseline, and later, to monitor progress.[45] However, since these tests measure recent substance use rather than chronic use or dependence, they are not recommended as screening tools.[45]
Mechanisms
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Main articles: Addiction § Mechanisms, and Substance dependence § Biomolecular mechanisms
Rehabilitation
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There are many underlying mechanisms behind the rehabilitation of SUD. Some include coping, craving, motivation to change, self-efficacy, social support, motives and expectancies, behavioral economic indicators, and neurobiological, neurocognitive, and physiological factors. These can be treated in a variety of ways, such as by cognitive behavioral therapy (CBT), motivational interviewing (MI), combined behavioral intervention (CBI), and more.[46]
Management
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Withdrawal management
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Depending on the severity of use, and the given substance, early treatment of acute withdrawal may include medical detoxification. Of note, acute withdrawal from heavy alcohol use should be done under medical supervision to prevent a potentially deadly withdrawal syndrome known as delirium tremens. See also Alcohol detoxification.
Therapy
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Main article: Drug rehabilitation
Therapists often classify people with chemical dependencies as either interested or not interested in changing. About 11% of Americans with substance use disorder seek treatment, and 40–60% of those people relapse within a year.[47] Treatments usually involve planning for specific ways to avoid the addictive stimulus, and therapeutic interventions intended to help a client learn healthier ways to find satisfaction. Clinical leaders in recent years have attempted to tailor intervention approaches to specific influences that affect addictive behavior, using therapeutic interviews in an effort to discover factors that led a person to embrace unhealthy, addictive sources of pleasure or relief from pain.