Substance use disorder is defined by 11 DSM-5 criteria organized in four clusters. Severity is determined by criterion count: 2-3 = mild, 4-5 = moderate, 6+ = severe. The same framework applies across substances; the criteria scale to the patient's specific substance and circumstances.
The four clusters:
Impaired control (4 criteria): taking more than intended; unsuccessful attempts to cut down; spending substantial time obtaining/using/recovering; craving.
Social impairment (3 criteria): failure to fulfill major role obligations; continued use despite social/interpersonal problems; giving up important activities.
Risky use (2 criteria): use in physically hazardous situations; continued use despite physical/psychological problems caused or worsened by use.
Pharmacological (2 criteria): tolerance (need more for same effect); withdrawal (characteristic syndrome on cessation, or use to relieve/avoid withdrawal).
The shared neuroanatomy: every substance reaches the same final common pathway — VTA dopamine flooding the nucleus accumbens, triggering reward learning that reorganizes the system over time. Different molecular routes converge on the same circuit. Combined with weakened PFC top-down control (often pre-existing vulnerability, often worsened by sustained use), the pattern that emerges is the addiction phenotype.
The framing matters. SUD is a chronic, relapsing brain disorder, not a character defect. The patient's brain has been reorganized by repeated reward-system activation. Evidence-based treatment substantially reduces mortality and improves functional outcomes. The disease framing is consistent with neurobiology and produces better clinical outcomes than moralized approaches.
Treatment framework: harm reduction (reduce immediate dangers without requiring abstinence — naloxone, safer use supplies, vaccination, treatment of complications), medication-assisted treatment (for substances where it exists — opioids, alcohol, tobacco), behavioral interventions (CBT for SUD, contingency management, motivational interviewing, 12-step facilitation), treatment of comorbid psychiatric and medical conditions, social support and recovery infrastructure (sober housing, peer support, employment support).
When you encounter a patient with substance use disorder, the framework matters more than any specific intervention. Chronic disease with episodic exacerbations — like diabetes or hypertension. Treatment works; relapses happen; ongoing support matters more than any single intervention.