Parkinsonism and psychopathology severity in real-world outpatients with schizophrenia: A cross-sectional PRISM study

Extrapyramidal symptoms (EPS) have been described as intrinsic to schizophrenia spectrum disorders (SSD), beyond medication-induced effects. Among EPS, parkinsonism is the most prevalent subtype and has been linked to poorer clinical and functional outcomes. We aimed to examine the relationships between parkinsonism and psychopathology and social functioning, as well as its demographic and pharmacological correlates, in a real-world sample of outpatients with schizophrenia receiving stable antipsychotic medication. Data were drawn from the PRISM project, an EU-funded, multicentre, cross-sectional, naturalistic study. Parkinsonism was assessed with the Extrapyramidal Symptoms Rating Scale (ESRS). Patients aged 18-45 years with a confirmed DSM-IV diagnosis of schizophrenia were included if clinically stable on unchanged antipsychotic dosage for ≥ 8 weeks and excluded if scoring > 22 on the PANSS-Positive subscale or ≥ 4 on the ESRS. Associations were analysed using correlation and regression models adjusted for relevant covariates, including antipsychotic exposure. Ninety patients were included (mean age 31.53 ± 6.64 years; 36.7% female; 27.8% "other than White"). Parkinsonism prevalence was 51% (ESRS≥1), higher among "other than White" participants (80% vs. 40%, χ²p < 0.001). Parkinsonism was not significantly associated with antipsychotic dose, route, or generation, nor with concomitant psychotropic use (all p > 0.05). Parkinsonism severity correlated with PANSS-Positive (rₛ = 0.228, p = 0.031), PANSS-Negative (rₛ = 0.278, p = 0.008), PANSS-General (rₛ = 0.210, p = 0.047), and PANSS-Total (rₛ = 0.283, p = 0.007). In adjusted regression models, associations remained significant for PANSS-Negative (β = 0.276, p = 0.019) and PANSS-Total (β = 0.234, p = 0.043). No significant associations were observed with social functioning. These findings suggest that parkinsonism is closely associated with clinical symptom severity and may reflect core illness-related features of schizophrenia.