Brain’s Stress Control Region Larger With Mood Disorders
People with depression or bipolar disorder were found to have a larger hypothalamus, compared with healthy control subjects, in a study published in Acta Psychiatrica Scandinavia. The brain region is associated with stress control.
Researchers used a high-resolution 7-Tesla magnetic resonance imaging (MRI) scanner to obtain brain images of 40 patients with major depressive disorder, half of whom were unmedicated, as well as 21 patients with bipolar disorder and 23 healthy control subjects.
In patients with either mood disorder, the left hypothalamus was approximately 5% larger, compared with the healthy controls, according to the study. The larger size was evident regardless of whether or not patients used medication.
“We observed that this brain region is enlarged in people with depression as well as in those with bipolar disorder, two types of affective disorders,” said researcher Stephanie Schindler, a PhD student at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, and the department of psychiatry and psychotherapy at the University Clinic in Leipzig.
The more severe the depression, the larger the hypothalamus, researchers observed in one of the patient groups with depression.
Depression is linked with a dysregulation of the endogenous stress response system, or hypothalamic-pituitary-adrenal axis, which is typically triggered by stress, researchers explained. In response to a threat, the system increases the amount of cortisol in the body. After the threat has passed, control mechanisms in the axis typically return the system to a more balanced state.
In people predisposed to depression, however, the stress response tends to continue. The underlying reason for the hyperactive stress response and the role of the hypothalamus in its control have been unclear, although researchers have theories.
“Higher activity could lead to structural changes,” said researcher Stefan Geyer, MD, of the Max Planck Institute for Human Cognitive and Brain Sciences, “and thus to a larger volume of the hypothalamus normally the size of a one-cent coin.”