Amygdala enlargement linked to future onset of depression

A neuroimaging study in Germany found that individuals who are about to develop depression tend to have higher gray matter volume of the amygdala brain region compared to both healthy individuals (not about to develop depression) and individuals already suffering from major depressive disorder. The research was published in Neuropsychopharmacology.

Depression, also known as major depressive disorder, is a mental health condition marked by persistent low mood, loss of interest or pleasure, and a range of emotional and physical symptoms. It affects how a person feels, thinks, and handles daily activities such as sleeping, eating, and working. To be diagnosed, symptoms must last at least two weeks and interfere with daily functioning.

Common symptoms include fatigue, difficulty concentrating, feelings of worthlessness or guilt, sleep disturbances, changes in appetite, and suicidal thoughts. Depression can range from mild to severe and may occur once or repeatedly over a lifetime. Brain changes involving neurotransmitters like serotonin and norepinephrine are often involved. Stress, trauma, chronic illness, or major life changes can also trigger depressive episodes.

Study author Anna Kraus and her colleagues wanted to explore whether individuals about to develop depression for the first time (referred to as converters) have some specificities in the brain structure that would allow the prediction of this condition in advance. They note that previous studies report lower gray matter volume in the brains of individuals with depression, but this was related to the number of recurrent depressive episodes and the duration of illness.

Study participants came from two large independent longitudinal studies – the Marburg-Münster Affective Disorders Cohort Study (MACS) and the Münster Neuroimaging Cohort (MNC). Both are ongoing neuroimaging studies including converters, patients with affective, psychotic, and anxious disorders and healthy individuals used as controls.

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Analysis for this study included 1279 participants from MACS and 430 from the MNC.  In the MACS dataset there were 30 converters, 590 patients with depression, and 659 healthy participants. The MNC sample contained 15 converters, 158 patients with depression, and 257 healthy individuals. All participants underwent neuroimaging.

Results showed that converters (individuals that later developed depression) tended to have higher gray matter volume of the amygdala region of the brain compared to both patients with depression and healthy individuals. It was also higher than that of patients with imminent recurrence of a depressive episode. Compared to healthy individuals, converters additionally had lower gray matter volume of the dorsolateral prefrontal cortex and insula regions. However, they did not differ in this from patients with depression. Gray matter volume is the total amount of brain tissue made up of neuronal cell bodies in a brain region.

“By examining one of the largest available converter samples in psychiatric neuroimaging, this study allowed a first determination of neural markers for an impending initial depressive episode. Our findings suggest a temporary vulnerability, which in combination with other common risk factors might facilitate prediction and in turn improve prevention of depression.”, study authors concluded.

The study sheds light on the brain structure specificities of individuals about to develop depression. However, it should be noted that the design of this study does not allow any causal inferences to be derived from the results.

The paper, “Brain structural correlates of an impending initial major depressive episode,” was authored by Anna Kraus, Katharina Dohm, Tiana Borgers, Janik Goltermann, Dominik Grotegerd, Alexandra Winter, Katharina Thiel, Kira Flinkenflügel, Navid Schürmeyer, Tim Hahn, Simon Langer, Tilo Kircher, Igor Nenadić, Benjamin Straube, Hamidreza Jamalabadi, Nina Alexander, Andreas Jansen, Frederike Stein, Katharina Brosch, Paula Usemann, Lea Teutenberg, Florian Thomas-Odenthal, Susanne Meinert, and Udo Dannlowsk.