Cortical structural alterations and thyroid autoantibodies underlying anxiety in major depressive disorder with...

Major depressive disorder (MDD) is often accompanied by anxiety and may co-occur with Hashimoto's thyroiditis (HT), an autoimmune thyroid disease linked to mood disturbances. Patients with comorbid HT often present with more severe anxiety, yet the neurobiological mechanisms underlying this comorbidity remain unclear.

The study included 44 MDD patients without HT (MDDHT-), 45 MDD patients with comorbid HT (MDDHT+), 48 HT patients, and 80 healthy controls (HC). Participants completed self-report questionnaires, blood sampling, and MRI scans. MDD patients were additionally evaluated with the Hamilton Depression (HAMD-17) and Anxiety (HAMA) Rating Scales. Cortical morphology was analyzed with FreeSurfer. Generalized linear models were employed to examine the main and interactive effects of MDD and HT, controlling for age, sex, eTIV, education, and medication load index. Partial correlation analyses were conducted to explore associations between cortical alterations and clinical measures.

Depression diagnosis was independently associated with reduced surface area in the left cuneus and pericalcarine gyrus, while HT was independently linked to reduced surface area in the left cuneus. Moreover, a significant interaction between depression and HT was observed in the surface area of the left middle temporal gyrus. In MDDHT+ patients, the left cuneus surface area was negatively correlated with anxiety/somatization factor and GAD-7 scores. Furthermore, Tg-Ab levels were positively correlated with anxiety/somatization factor and GAD-7 scores in the MDDHT+ group.

MDD and HT exert distinct effects on cortical surface area. These alterations, together with Tg-Ab levels, may jointly contribute to anxiety symptoms in MDDHT+ patients.