The left side of the hypothalamus was revealed to be 5 percent larger in a new study of people with affective disorders such as depression and bipolar.
hypothalamus cross section

New research emphasizes the role of the hypothalamus (depicted here) in depression and bipolar disorder.

Over 16 million adults in the United States have had at least one episode of major depression during the past year.

In fact, depression is one of the most prevalent mental health problems in the U.S.

At least 9 million more people aged 18 and over are living with bipolar disorder, according to the National Institute of Mental Health.

The precise underlying causes for both of these conditions remain unknown, but neuroscientists are unraveling more and more aspects that can affect a person’s chances of developing these disorders.

Left hypothalamus 5 percent larger

Schindler and her team examined the brains of 84 people, of whom: 20 had depression but did not take any medication for it, 20 had depression but also took medication, 21 lived with bipolar, and 23 were controls who did not have an affective disorder.

They used MRI to study the participants’ brains and high‐precision volumetry to determine the size of their hypothalami.

Overall, they saw that people with an affective disorder had a 5 percent increase in the volume of the left side of their hypothalamus, on average.

We observed that this brain region [the hypothalamus] is enlarged in people with depression as well as in those with bipolar disorder, two types of affective disorders.”

Stephanie Schindler

Importantly, in the case of people with depression, hypothalamus size correlated directly with the severity of the condition.

Medication did not affect the size of the brain region. The researchers warn that beyond the links they found, not much can be inferred on the causality underlying the findings.

“Higher activity could lead to structural changes and thus to a larger volume of the hypothalamus normally the size of a one-cent coin,” explains study co-author Stefan Geyer.

The authors write, “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.”

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