Background: Specialised addiction treatment centers (SAC) and general mental health centers (GMHC) both offer care to people with substance use disorders (SUD) in Belgium, but these sectors often operate in parallel, with little collaboration. This fragmented system may lead to inefficiencies, particularly in the treatment of individuals with dual diagnoses. Despite the recognized challenges, there is limited understanding of the factors that influence whether patients with SUD are treated in SAC or GMHC.

Objectives: This observational study has two main objectives: METHODS: The study used routinely collected data from treatment centers in Belgium from 2019 (Belgian Treatment Demand Indicator). Logistic regression evaluated the weight of drug use and sociodemographic variables for people entering treatment for SUD for the first time (n = 8322). A random forest algorithm was used to study all patients' orientation toward both sectors, across all treatment episodes (n = 29,658).

Results: The study found that the primary substance significantly influences sector choice. Patients using illicit substances like cannabis, opiates, cocaine, and stimulants are 6-12 times more likely to be treated in an SAC than those using alcohol. Factors such as income source and referral source (e.g. self-referral, general practitioner, etc) also significantly impact patient orientation.

Conclusion: These findings highlight the need for better integration between SAC and GMHC to adequately address the complex needs of people with SUD, especially with dual diagnosis.