Substance Use Disorders

Substance use disorders are conditions in which recurrent use of alcohol or other drugs leads to clinically significant impairment, including impaired control, continued use despite harm, and physiological features such as tolerance and withdrawal. Often co-occurring with other psychiatric disorders, they are a major focus of mental health and addiction nursing.

Definition

Substance use disorders are diagnosed when a problematic pattern of substance use causes clinically significant impairment or distress, reflected in symptoms across impaired control, social impairment, risky use, and pharmacological criteria (tolerance and withdrawal); severity is graded by the number of criteria met.

Scope

This topic covers the definition and diagnostic features of substance use disorders, the concept of addiction as a relapsing brain-related condition, epidemiology and burden, explanatory models, comorbidity (dual diagnosis), and relevance to nursing care. It is reference-educational and does not provide dosing, withdrawal-management, or individualised treatment instructions.

Core questions

• What distinguishes a substance use disorder from substance use itself?
• How does the brain-disease model conceptualise addiction?
• Why are substance use disorders so often comorbid with other psychiatric conditions?
• What is meant by dual diagnosis, and why does it complicate care?

Key concepts

• Impaired control over use
• Tolerance
• Withdrawal
• Craving
• Continued use despite harm
• Relapse
• Dual diagnosis (comorbidity)
• Harm reduction

Key theories

Brain-disease model of addiction

Conceptualises addiction as a chronic, relapsing condition involving drug-induced changes in brain reward, motivation, and self-control circuits, reframing it as a treatable health condition rather than a purely volitional or moral problem.

Three-stage neurocircuitry model

Describes addiction as a cycle of binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation, each linked to specific neurocircuits, explaining the compulsion and relapse that characterise the disorder.

Mechanisms

Substance use disorders involve repeated exposure to drugs of misuse that act on brain reward and stress systems, producing neuroadaptations in dopaminergic reward, extended-amygdala stress, and prefrontal executive-control circuits. These changes are described as a cycle of intoxication, negative-affect withdrawal, and craving-driven preoccupation, which underlies the compulsive use and high relapse risk that frame the chronic, relapsing-remitting course addressed in care. Mechanisms interact with genetic, developmental, and social vulnerability.

Clinical relevance

Nurses encounter substance use disorders across emergency, medical, psychiatric, and community settings, where non-judgemental engagement, screening, recognition of intoxication and withdrawal, and attention to co-occurring mental and physical illness are central. Dual diagnosis - a substance use disorder alongside another psychiatric disorder - is common and shapes assessment. This entry orients to the disorder group and is not a basis for individual treatment, detoxification, or prescribing decisions.

Epidemiology

Alcohol and other substance use disorders affect a substantial share of the population, contribute heavily to the global burden of disease through both direct effects and associated injury and illness, and frequently co-occur with mood, anxiety, and psychotic disorders. Illicit drug use and dependence alone account for a significant proportion of years lived with disability worldwide.

Evidence & guidelines

Diagnosis follows the DSM-5-TR (substance use disorders) and ICD-11 (disorders due to substance use, block 6C4Z); burden estimates come from the Global Burden of Disease programme. Substance-specific screening, withdrawal, and treatment detail belong in dedicated clinical guidelines rather than this reference entry.

History

Conceptions of problematic substance use shifted over the twentieth century from moral and purely legal framings toward medical models; the DSM-5 merged the earlier "abuse" and "dependence" categories into a single graded substance use disorder, and neuroscience advanced the brain-disease model of addiction.

Debates

Is the brain-disease model the best framing of addiction?

While influential in reducing stigma and supporting treatment access, the brain-disease model is debated by those who emphasise social, behavioural, and choice-related dimensions of substance use, a tension relevant to how nurses understand and engage with people who use substances.

Seminal works

• volkow-2016
• koob-volkow-2016
• apa-dsm5tr-2022

Frequently asked questions

What is the difference between using a substance and having a substance use disorder?

A disorder is diagnosed only when use becomes a problematic pattern that causes clinically significant impairment or distress - such as impaired control, continued use despite harm, or withdrawal - not simply because a substance is used.

What does "dual diagnosis" mean?

Dual diagnosis refers to having a substance use disorder together with another psychiatric disorder, such as depression or psychosis; this combination is common and is important to recognise because each condition can affect the other.