Evaluating the Prodromal Questionnaire-16 for Screening and Prediction of Psychosis in Autistic Adults: Cross-Sectional and Longitudinal Findings From a National Cohort.

BACKGROUND AND HYPOTHESIS: Autistic individuals are at elevated risk for psychosis, yet attenuated psychotic symptoms may go undetected due to overlapping features and limited validation of screening tools in autistic populations. This study evaluated the performance of the Prodromal Questionnaire-16 (PQ-16) in autistic adults, including its longitudinal predictive value for schizophrenia-spectrum diagnoses, and examined demographic and clinical correlates of attenuated psychotic symptoms. STUDY DESIGN: Using data from a large longitudinal cohort (the Netherlands Autism Register), we analyzed self-reported PQ-16 symptom and distress scores alongside demographic variables, age at autism diagnosis, autistic traits (AQ-28), and depressive symptoms (PHQ-Dep-4). Descriptive analyses characterized PQ-16 score distributions. Linear regression models examined predictors of PQ-16 symptom severity. Logistic regression and ROC analyses evaluated whether PQ-16 scores predicted self-reported new-onset schizophrenia-spectrum diagnoses at follow-up. STUDY RESULTS: Among 1686 autistic adults (mean age = 46.04), 34.1% exceeded the PQ-16 cutoff (≥6), indicating a substantially higher prevalence of attenuated psychotic symptoms than reported in non-autistic populations. In the fully adjusted model, higher PQ-16 scores were independently associated with greater autistic trait severity and depressive symptoms. New-onset schizophrenia-spectrum diagnoses based on self-report occurred in 1.4% of participants with longitudinal data (5/361) and were observed exclusively among individuals above the PQ-16 cutoff (3.2% vs 0.0%, P = .015). ROC analyses suggested apparent discrimination for PQ-16 total, distress, and combined scores, although estimates should be interpreted cautiously given the very small number of incident cases. CONCLUSIONS: The PQ-16 identifies meaningful patterns of attenuated psychotic symptoms in autistic adults. Findings support brief screening as part of a 2-step assessment approach.