Antipsychotic response in delusional disorder and schizophrenia: a prospective cohort study

Scientific evidence focused on the treatment response in delusional disorder (DD) patients is scarce, and the findings are controversial. Our goal was to compare the antipsychotic response at the 12-week followup between patients diagnosed with DD and patients diagnosed with schizophrenia and to identify potential response dimensions.

A prospective, observational, cohort study with 12-week follow-up was conducted with DD and schizophrenia patients matched for sex, age and cumulative years of disease. The following scales were assessed: Positive and Negative Syndrome Scale (PANSS; 5-factors), Personal and Social Performance Scale (PSP), Clinical Global Impression Scale (CGI), and Columbia-Suicide Severity Rating Scale (C-SSRS). Treatment response was defined as a ≥30% reduction in the total PANSS score. Linear and logistic regression models were used to investigate the potential predictive value of psychopathological variables for the antipsychotic response.

Response percentages in DD and schizophrenia were 61.5% and 69.2%, respectively. The duration of untreated psychosis, antipsychotic dosage, and diagnosis did not predict antipsychotic response. In the whole sample, improvement in positive symptoms was significantly associated with the clinical global improvement (p=0.006), explaining almost 20% of the variance in the model. Within the DD group, improvement in cognitive symptoms explained 30% of the variance in clinical global improvement.

Both response percentages and required antipsychotic doses were similar between DD and schizophrenia. Changes in positive symptoms were associated with clinical global improvement in the entire sample, and improvement in cognitive symptoms was correlated with global improvement exclusively in DD.