Clinical outcomes and diagnostic stability in first-episode other specified schizophrenia spectrum and other psychotic disorder: evidence for a distinct clinical entity

Research on the clinical outcomes and diagnostic stability of first-episode other specified schizophrenia spectrum and other psychotic disorder (FE-OSSO) remains very limited. This study was conducted to identify baseline demographic and clinical features and cognitive function, as well as 2-year outcomes of patients with FE-OSSO compared with those with first-episode schizophrenia (FE-SZ). The study subjects were 100 patients with FE-OSSO and age- and sex-matched 110 patients with FE-SZ. Four OSSO subtypes were classified according to the clinical manual. We compared clinical variables, cognitive function, and 2-year outcomes (treatment response, remission/recovery, compliance, drop out, relapse) between the two groups. In addition, diagnostic stability was ascertained over the 2-year follow-up. Patients with FE-OSSO had lower symptom severity, lower medication doses, greater rumination and higher cognitive functioning than those with FE-SZ. They also exhibited lower proportion of good compliance and higher rates of partial remission at the 1-year and/or 2-year follow-up compared with those with FE-SZ. Diagnostic stability was substantially high, 91.1%, during the 2-year follow-up. These findings indicate that OSSO has unique clinical features and high diagnostic stability, suggesting that it should be treated as a distinct clinical entity. The next phase of early intervention should focus on preventing the progression from OSSO to more severe illness, SZ, by identifying which OSSO cases are at highest risk of conversion to SZ.