Cortical thickness abnormalities in bipolar disorder patients with a lifetime history of auditory hallucinations

Objectives We aimed to investigate morphometric correlates of auditory hallucinations in bipolar disorder ( BD ) by comparing cortical thickness and cortical surface area in bipolar disorder patients with ( BD +) and without ( BD −) a lifetime history of auditory hallucinations. Based on previous findings in schizophrenia patients, we hypothesized that the cortex would be thinner in the auditory cortex in BD + compared to BD −. Methods Bipolar disorder spectrum (n = 157) patients and healthy controls (n = 279) underwent 1.5T magnetic resonance imaging ( MRI ) scanning. Hypothesis‐driven analyses of cortical thickness and surface area in regions of the auditory cortex (Heschl's gyrus [ HG ], planum temporale and superior temporal gyrus) were conducted comparing BD + (n = 49) and BD − (n = 108) using linear regression models, covaried for age and sex. Furthermore, we explored vertex‐wise group differences in thickness and surface area across the whole cerebral cortex. Results Hypothesis‐driven analyses: BD + had significantly thicker cortex in the left HG compared to BD − ( B  = 0.128, P  = .0046). The finding was not explained by duration of illness, global functioning, bipolar subtype, IQ or use of antipsychotic, antidepressant or antiepileptic medication, or by lithium. Exploratory analyses: A small region of thicker cortex in BD + compared to BD − was seen in the left superior parietal lobule (false discovery rate <0.05). There were no significant group differences in cortical surface area. Conclusion A lifetime history of auditory hallucinations in BD was associated with cortical thickness alterations in both the left HG and the superior parietal lobule. Contrary to our hypothesis, BD + showed thicker, rather than thinner cortex compared to BD −. Replications in independent samples are needed.