A level of D(2) receptor occupancy between 60% and 70% is optimal for subjective experience of patients with recent-onset schizophrenia. Substantial interindividual variation in D(2) receptor occupancy was seen at fixed low-dose levels of olanzapine and haloperidol. Olanzapine, 7.5 mg/day, showed no superior subjective response over haloperidol, 2.5 mg/day. Olanzapine may need to be dosed higher than 7.5 mg/day for most patients with recent-onset schizophrenia, and haloperidol needs to be individually titrated in the very low dose range to reach optimal occupancy.

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Aim: Clinical staging of schizophrenia entails a new method that identifies clusters of symptoms and variation in level of remission, with the goal to create a framework for early intervention. Additionally, duration of untreated psychosis (DUP) may influence symptom severity in the first episode of psychosis (FEP) and could necessitate refining of the staging model. However, consistent evidence concerning variation in symptom severity and DUP between stages is missing. Therefore, we evaluated the clinical validity of the staging model by investigating differences in symptom severity across stages in schizophrenia spectrum disorders. Second, we assessed if a prolonged DUP is associated with higher symptom severity in FEP. Methods: We performed a cross-sectional study of 291 acutely admitted patients with a schizophrenia spectrum disorder. Patients were assigned to clinical stages following the definition of McGorry. Symptom severity was evaluated with the new DSM-5 Clinician-Rated Dimensions of Psychosis Symptom Severity (CRDPSS). In FEP, we determined the DUP. Results: Significantly higher severity scores of CRDPSS items hallucinations