A new study developed by the University Hospital of Leipzig (Germany) has found that the left side of the hypothalamus (the one associated with the regulation of stress) is 5% larger in people with affective disorders such as depression and bipolar disorder.
Depression is one of the most prevalent mental health problems in society.
The precise origin for these two conditions remains unknown, but scientists continue to investigate and find more and more aspects that can affect a person’s chances of developing these disorders.
The neurobiological roots of depression
Functional magnetic resonance and other new imaging techniques have enabled researchers to locate various areas of the brain and neural networks involved in affective disorders . For example, in the case of depression, several studies have found that treatment-resistant depression is associated with a decrease in the volume of the hippocampus and a smaller amygdala.
The hippocampus is an area heavily involved in memory formation and learning, while the amygdala is a small brain structure responsible for emotional processing and responding to what is perceived as danger or stress.
In fact, the entire endocrine stress response system is disrupted in people with depression. The axis between the hypothalamus, the pituitary gland, and the adrenal glands is overactive.
In the case of people with depression, these structures are in “overload” even in the absence of objective danger. The present investigation aimed to clarify the role of the hypothalamus in this hyperactive chain reaction.
The volume of the hypothalamus
The experts examined the brains of 84 people , of whom 20 had depression but did not take any medication, 20 had depression if they took medication, 21 lived with bipolar disorder and 23 were control subjects without any affective disorder.
They used magnetic resonance imaging to study the participants’ brains and high-precision volumetry to determine the size of their hypothalamus. Overall, they found that people with an affective disorder had 5% more volume on the left side of their hypothalamus, on average.
“We observed that this region of the brain [the hypothalamus] is enlarged in people with depression, as well as in those with bipolar disorder , two types of affective disorders,” explains Stephanie Schindler, leader of the work that publishes the journal A cta Psychiatrica Scandinavica.
Importantly, in the case of people with depression, the size of the hypothalamus is directly correlated with the severity of the condition.
The medication did not affect the size of the brain region. The researchers caution that beyond the links they found, not much can be inferred about the causality underlying the findings.
“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 for the hypothalamus in mood disorders,” the authors conclude.
Reference: Hypothalamus enlargement in mood disorders. S. Schindler L. Schmidt M. Stroske M. Storch A. Anwander R. Trampel M. Strauß U. Hegerl S. Geyer P. Schönknecht. 2018
https://doi.org/10.1111/acps.12958 Acta Psychiatrica Scandinavica.
