PsychoPharm aggregated risk score (PARS): a multidimensional tool to flag high-risk pharmacotherapy in psychiatric patients.

Introduction: Psychiatric outpatients frequently receive complex, long-term regimens where polypharmacy, drug-drug interactions (DDIs), QT interval risk, anticholinergic load, and serotonergic exposure co-occur. Clinicians must triage drug lists quickly, yet most tools address a single risk domain. We developed the PsychoPharm Aggregated Risk Score (PARS), a visit-level composite score that integrates multiple pharmacological risk domains into a single, clinically interpretable signal. Methods: We analyzed 2,666 visits from 680 adults in ambulatory psychiatry. For each visit, we computed the risk components: DDI score from DrugBank, AZCERT QT risk, anticholinergic cognitive burden (ACB), serotonergic exposure, and polypharmacy ( Results: The prevalence of high-risk cases was observed in 25.2% of visits. Across validation schemes, the primary 80-20 patient-level split achieved the best accuracy, precision, and F1 at the 0.30 operating point. In the primary 80-20 split stratified by High-risk status, the logistic model achieved an AUC of 0.931 (patient-bootstrap 95% CI 0.875-0.971). Discrimination was similar with additional age and sex stratification (AUC of 0.938) and 5-fold GroupKFold (pooled out-of-fold AUC 0.939), indicating robustness to partitioning. In the drug-only model, positive associations included drugs such as quetiapine, haloperidol, clozapine, and amiodarone. The highest-ranked visits combined central nervous system-heavy regimens and polypharmacy. Conclusion: As an exploratory tool, PARS integrates DDIs, QT risk, anticholinergic cognitive burden, serotonergic exposure, and polypharmacy into a single probability that reliably discriminates High-risk visits and supports screening at a 0.30 operating threshold. Our approach highlights actionable drug combinations and patient profiles for drug review and deprescribing.