Cortical thinning in young psychosis and bipolar patients correlate with common neurocognitive deficits

BACKGROUND People in midlife with established psychosis or bipolar disorder exhibit patterns of cortical thinning across several brain regions. It is unclear whether these patterns are indicative of a continuously active pathological process, residual effects of an earlier illness phase or pre-illness onset developmental risk factors. Here, we investigated whether cortical thinning is evident in younger patients in the early phase of psychosis or bipolar disorder and the relationship between cortical thinning and neurocognitive performance in young people. METHODS Magnetic resonance imaging was obtained from a sample of young patients with psychosis (n = 40; mean age 23.5 years), bipolar disorder (n = 73; mean age 21.9 years) or controls (n = 49; mean age 24.2 years). Group differences in cortical thickness were assessed using statistical difference maps, and regions of cortical thinning were correlated with medication dosage and performance on neurocognitive tasks. As initial comparisons using multiple corrections found no differences between the groups, follow-up analysis with a significance threshold of p < 0.001 was performed. RESULTS AND DISCUSSION As distinct from reported findings in older subjects, young patients with psychosis have less extensive thinning in parietal-temporal areas and do not demonstrate significant thinning in the insula or dorsal lateral prefrontal cortex. Young patients with bipolar disorder exhibit cortical thinning in regions more consistent with those previously reported in paediatric bipolar patients. Although there were some differences in the regions of cortical thinning between the two groups, the shared regions of cortical thinning were correlated with neurocognitive deficits in visual sustained attention, semantic verbal fluency and verbal learning and memory that are commonly reported in young people with either psychosis or bipolar disorder.