Hypothalamus enlargement in mood disorders

Objective The purpose of this study was to determine, in vivo, whether the hypothalamus volume is reduced in patients with mood disorders. Methods The cross-sectional study included 20 unmedicated (MDDu) and 20 medicated patients with major depressive disorder, 21 patients with bipolar disorder, and 23 controls. Twenty of the controls were matched to the MDDu. Seven Tesla, T1-weighted magnetic resonance images were acquired and processed using methods specifically developed for high-precision volumetry of the hypothalamus. Results An overall group difference was observed for the left hypothalamus volume corrected for intracranial volume. Planned contrasts identified that the left hypothalamus was approximately 5% larger in each patient group compared with the control group. A paired t-test with the 20 matched pairs of MDDu and controls and without correction for covariates confirmed the larger left hypothalamus volume in MDDu. Conclusions Contrary to our expectations, the hypothalamus volume was increased in patients with uni- and bipolar affective disorders. The effect was left-sided and independent of medication status or statistical correction for covariates. Supported by emerging evidence that the stress response may be related to structural and functional asymmetry in the brain, our finding suggests a crucial role of the hypothalamus in mood disorders.