Chapter 67: Substance-Related and Addictive Disorders

The diagnostic framework from the DSM-5-TR defines these disorders through compulsive use patterns, continued engagement despite harmful consequences, and functional impairment. Prevalence varies substantially by substance type, with alcohol use disorder affecting millions while opioid use disorder and cannabis dependence represent growing public health concerns, particularly following the COVID-19 pandemic. Understanding these conditions requires integration of genetic, neurobiological, and environmental factors. Genetic vulnerability, including single nucleotide polymorphisms in genes such as ADH1B, interacts with psychosocial stressors through mechanisms described by the stress-diathesis model. At the neurobiological level, chronic substance exposure dysregulates reward circuits and neural systems controlling impulse control and habitual behavior, affecting structures like the anterior cingulate cortex and orbitofrontal cortex. Clinical presentations differ significantly by substance class. Alcohol intoxication and withdrawal present distinct risks, with severe withdrawal capable of causing life-threatening delirium tremens. Opioid overdose manifests through respiratory depression while withdrawal produces painful but generally non-lethal symptoms. Stimulants generate cardiovascular complications and psychotic features, while sedative-hypnotic withdrawal constitutes a medical emergency requiring supervised management. Special populations including adolescents whose brains undergo development until age twenty-five and geriatric patients experiencing polypharmacy require tailored diagnostic and treatment approaches. Primary care settings serve as optimal locations for implementing the SBIRT framework encompassing screening, brief intervention, and treatment referral. Evidence-based treatment incorporates medication-assisted therapy using agents like buprenorphine and naltrexone, motivational interviewing techniques, cognitive behavioral therapy, and harm reduction strategies including naloxone distribution. Language choice matters clinically and ethically, with person-first terminology and accurate clinical descriptors reducing stigma and improving treatment engagement and outcomes.