Cortical thickness is associated with poor insight in first-episode psychosis

Abstract

Through conceptualizing poor insight in psychotic disorders as a form of anosognosia (neurological deficit), frontal lobe dysfunction is often ascribed a vital role in its pathogenesis. Whether non-frontal brain regions are important for insight remains to be investigated. We used a multi-method approach to examine the neural morphometry of all cortical regions for insight in first-episode psychosis. Insight was rated in 79 people with a first-episode psychosis with the awareness of illness and awareness of treatment need and efficacy items of the Scale for assessment of Unawareness of Mental Disorder. Participants were assessed with magnetic resonance imaging. Cortical thickness analysis and voxel-based morphometry were utilized to identify the possible neuroanatomical basis of insight. Cortical thickness technique revealed that poorer awareness of illness was associated with regional thinning in left middle frontal and inferior temporal gyri. Poorer awareness of treatment need and efficacy was associated with cortical thinning in left medial frontal gyrus, precuneus and temporal gyri. No significant associations emerged between any insight measure and gray matter density using voxel-based morphometry. The results confirm predictions derived from the anosognosia/neuropsychology account and assert that regional thickness in frontal cortex is associated with awareness of illness in the early phase of psychosis. The fact that prominent thickness reductions emerged in non-frontal regions of the brain in parietal and temporal cortices for both awareness of illness and awareness of treatment need and efficacy suggests that the neural signature of insight involves a network of brain structures, and not only the frontal lobes as previously suggested.