Cannabis Use Disorder in the Era of Legalization: Implications for Addiction Treatment Systems.

Introduction: Cannabis legalization has expanded rapidly across high-income jurisdictions, altering patterns of cannabis use, product potency, and commercial markets. Although surveillance systems increasingly quantify cannabis exposure, clinically meaningful harm is more difficult to detect. Cannabis use disorder (CUD) represents a key construct linking exposure to sustained impairment, yet its epidemiologic visibility depends heavily on diagnostic frameworks and measurement design. Aim: This review examines how contemporary surveillance systems detect cannabis-related harm and evaluates the implications of diagnostic classification, epidemiologic measurement, and treatment capacity for understanding and responding to CUD in the post-legalization era. Methods: We conducted a narrative review synthesizing literature on cannabis legalization, psychiatric epidemiology, and treatment of CUD. Evidence was identified from biomedical databases, epidemiologic surveys, systematic reviews, randomized trials, and policy analyses. Sources were examined across three domains: (1) post-legalization surveillance of cannabis exposure and harm, (2) diagnostic evolution and measurement of CUD in population surveys, and (3) current evidence for treatment interventions and treatment system responses. Results: Population surveillance systems measure cannabis exposure with increasing precision but show limited sensitivity for persistent or clinically meaningful harm. Transitions from DSM-IV's hierarchical abuse-dependence framework to the dimensional DSM-5 model expanded detection of mild and moderate disorder and altered prevalence estimates across epidemiologic surveys. International studies using DSM-5-aligned instruments generally report past-year CUD prevalence of approximately 2-3% in the general population, with substantially higher conditional risk among frequent users. However, surveillance systems relying on legacy diagnostic modules or restrictive assessment logic may underestimate disorder prevalence despite rising cannabis exposure and increasing acute health-care encounters. Evidence for CUD treatment indicates modest but consistent benefits from psychosocial interventions-including motivational, cognitive-behavioral, and contingency-based approaches-while no pharmacotherapies are currently approved, and treatment engagement remains low relative to estimated prevalence. Conclusion: Apparent uncertainty in post-legalization health outcomes often reflects limitations in measurement rather than absence of harm. Aligning surveillance systems with contemporary diagnostic frameworks and strengthening treatment pathways are essential for translating exposure monitoring into effective public health response. As legalization continues to expand, CUD provides an important test of whether addiction treatment systems can adapt to legalized substances whose harms are diffuse, chronic, and frequently under-recognized.