Distinguishing schizophrenia spectrum from non-spectrum disorders among young patients with first episode psychosis and at high clinical risk: The role of basic self-disturbance and neurocognition.

Introduction: The distinction between the schizophrenia spectrum and other types of disorders may be clinically relevant in terms of its predictive validity as suggested by studies showing schizophrenia spectrum patients have more unfavourable outcomes compared to other psychotic disorders. The present study aimed to investigate whether basic self-disturbances and neurocognitive processes that have been linked to psychosis risk have discriminative power for schizophrenia spectrum disorders in patients presenting with first episode psychosis (FEP) and at ultra-high risk for psychosis (UHR).

Methods: 38 FEP patients, 48 UHR patients, and 33 healthy controls were assessed for basic self-disturbances (using the Examination of Anomalous Self-Experience, EASE, interview), source monitoring and aberrant salience (behavioural tasks to measure neurocognitive constructs). Clinical groups were divided into patients with schizophrenia spectrum disorders and those with other non-spectrum disorders and were further compared on measures controlling for symptom severity and age.

Results: Basic self-disturbances distinguished schizophrenia spectrum from non-spectrum disorders in the 'FEP only' sample, F = 19.76, p < 0.001, η = 0.37, and also in the combined UHR/FEP sample, F = 23.56, p < 0.001, η = 0.22. Additionally, some processes related to source monitoring deficits were elevated in schizophrenia spectrum disorders. In contrast, the two groups (schizophrenia spectrum vs other diagnoses) performed similarly in aberrant salience tasks. Comparable results were obtained for analyses performed with an FEP/UHR combined sample and the 'FEP only' sample.

Discussion: Basic self-disturbances at the phenomenological level and source monitoring deficits on the neurocognitive level may be useful in identifying risk of schizophrenia spectrum disorders at the earliest clinical presentation.