Substance use disorders and use of somatic health services among forensic psychiatric patients: a nationwide register-based cohort study

BACKGROUND: Substance use disorders (SUD) are prevalent among forensic psychiatric patients and contribute to a complex mental and somatic health burden. While barriers to healthcare access are well documented, little is known about how individuals with comorbid SUD use general practitioner (GP) and acute somatic hospital services before entering forensic psychiatric treatment. AIMS: To examine the association between SUD and use of GP and acute outpatient hospital services. METHODS: We identified all individuals with a forensic psychiatric measure initiated in 2021-2022 from the Danish National Patient Register. SUD was defined as any ICD-10 F1 diagnosis, excluding acute intoxication, recorded during 2013-2017. Outcomes were GP consultations and acute outpatient hospital contacts during 2018. Associations were examined using negative binomial regression adjusted for age, sex, region, and prior-year service use. RESULTS: The cohort included 829 patients (39% with SUD). Almost all had ≥1 GP contact in 2018 (90% vs 89%). SUD was not associated with GP utilization (adjusted IRR = 0.99, 95% CI: 0.88-1.12). Acute outpatient contacts were more frequent among patients with SUD (45% vs 32%), with higher rates (IRR = 1.43, 95% CI: 1.04-1.97), attenuating after adjustment for prior-year use (aIRR = 1.28, 95% CI: 0.97-1.68). CONCLUSIONS: Forensic psychiatric patients with SUD had greater use of acute outpatient hospital services, but similar GP utilization, compared with those without SUD, suggesting reliance on crisis-driven rather than preventive care.