M175. BRAIN STRUCTURAL CORRELATES OF FUNCTIONAL CAPACITY IN FIRST-EPISODE PSYCHOSIS

BACKGROUND: Impaired functional capacity is a core feature of schizophrenia and present even in first episode psychosis (FEP) patients. Impairments in daily functioning tend to persist despite antipsychotic therapy but their neural basis is not clear. Previous studies suggest that volume loss in frontal cortex might be an important contributor but findings are inconsistent. We aimed to comprehensively investigate the brain structural correlates of functional capacity in first episode psychosis using MRI and a reliable objective measure of functioning (University of California, San Diego Performance-Based Skills Assessment (UPSA)) METHODS: In FEP and a well-matched control group, we measured cortical thickness, gray matter volume, and white matter tract integrity (fractional anisotropy, FA) in specific regions implicated by previous work. Between-group differences in these parameters were assessed first. We then examined correlations between MRI measures and UPSA scores in the FEP group while controlling for negative symptomology and medication use. RESULTS: The FEP group had thinner cortex in various frontal regions, fusiform, and insula, and reduced FA in inferior longitudinal fasciculus. In FEP, poorer functioning (UPSA) correlated with reduced superior frontal volume and lower FA in inferior longitudinal fasciculus. DISCUSSION: In accordance with previous findings, FEP exhibited widespread brain structural differences compared to controls. Importantly, frontal brain volumes and integrity of the inferior longitudinal fasciculus were identified as the structural correlates of functional capacity in FEP, after controlling for other relevant factors. These findings enhance mechanistic understanding of functional capacity deficits in schizophrenia by specifying the underlying neural correlates. In future, this could help inform intervention strategies.