Short-term outcome of first episode delusional disorder in an early intervention population

Background: Previous evidence suggests that delusional disorder has a later onset and better functional outcomes compared to schizophrenia. However, studies have not examined longitudinal outcomes in a first episode population, where confounding factors may be adjusted for. Methods: A nested case control study was designed within the National EDEN study; a cohort of 1027 first episode psychosis patients. Patients with a baseline diagnosis of delusional disorder (n = 48) were compared with schizophrenia (n = 262) at 6 and 12 months with respect to symptomatic and functional outcomes. Regression analysis was used to adjust for possible confounders. Results: Delusional disorder patients had a shorter duration of untreated psychosis compared to schizophrenia but were similar in other baseline characteristics. At baseline, delusional disorder patients had lower symptom scores but higher function scores compared to those with schizophrenia. At 12 months the differences persisted for symptoms scores but not overall function scores. After adjusting for baseline score, age and duration of untreated psychosis, differences between the groups remained significant only for Positive and Negative Syndrome Scale (PANNS) negative, general and total scores and recovery rates. There were no differences in changes in outcomes scores. Conclusions: Delusional disorder in a first episode psychosis population presents with less severe symptoms, higher recovery rates and better functioning than schizophrenia, but at 12 months differences are ameliorated when adjusting for baseline differences.