Neurocognition, social cognition and structural brain imaging in euthymic individuals with bipolar disorder and their first degree relatives

Background and aim: The relationship between the genetic roots of bipolar disorder (BD) and the impairments in neurocognitive and social cognitive domains along with the changes in the structural brain properties in bipolar disorder has not been elucidated yet. The aim of this study was to investigate the relationship between genetic liability to BD and such impairments, independent from the course of the illness and any effects of drug use, by comparing individuals at risk for BD, patients with BD, and healthy controls. Methods: 24 euthymic patients with BDI, 16 healthy siblings and 24 healthy controls were included in this study. The participants completed a test battery measuring neurocognition and social cognition after being assessed with a structured interview for DSM IV and underwent 3Tesla magnetic resonance imaging (MRI). For processing and analysis of the brain imaging data, CAT12 running within SPM12 was used. ANOVA was used for the intergroup comparisons of the cortical thickness measurements, of the scores from the cognitive tests and of the continuous demographic variables, and chi-square test was used for the categorical variables. Results: The scores of the patients on visual memory and mental state decoding and the siblings on mental state reasoning were found to be significantly lower than the scores of the healthy controls. The cortical thickness of the patients were lower in superior frontal gyrus and precentral gyrus; and the siblings in the inferior temporal gyrus and postcentral gyrus compared to the healthy controls. In addition, it was found that the cortical thickness of the healthy siblings were greater in the rostral middle frontal gyrus and the medial orbitofrontal cortex compared to the patients with BDI. Conclusion: The findings of this study provide data as evidence of impairment in visual memory in BDI and social cognition in BDI and siblings when compared to healthy individuals. The intergroup differences of cortical thickness are considered not only to be indicative of early signs of a brain structure that can be used for early diagnosis of BDI; but also related to the resistance markers.