Anxiety and depression symptoms in major depression and post-traumatic stress disorder reflect abnormal connections to the same emotion center in the brain, researchers have found.

Although major depression is common among individuals with PTSD, few studies have looked for underlying brain features that may contribute to both disorders. In this study, a research team found that for both disorders, more severe depression symptoms meant fewer connections between different brain regions and the amygdala. The amygdala is crucial for integrating emotional experience.

Reporting these findings online September 29 in Molecular Psychiatry, the team was led by NARSAD Scientific Council Member Yvette I. Sheline, M.D., recipient of a 1998 Young Investigator grant as well as 2002 and 2005 Independent Investigator grants, and first author Theodore D. Satterthwaite, M.D., a 2010 Young Investigator grantee M.A., both of the University of Pennsylvania, also included and 2007 Young Investigator grantee Charles R. Conway, M.D.

This study looked exclusively at women with depression or PTSD; all of the PTSD patients involved were women who had experienced intimate partner violence. They had not taken any psychiatric medication for at least three weeks before testing, making it less likely the study’s findings stem from medication use. Within this population, depression severity correlated with fewer connections between the amygdala and three other brain regions: the dorsolateral prefrontal cortex, important for evaluating risk and moral decisions; the anterior cingulate cortex, associated with decision making as well as regulating emotion and physiological processes like heart rate; and the anterior insula, which helps build the basis for all subjective experiences of the body (likely including emotional experience).

While reduced amygdala connections were linked to depression, the researchers found that more severe anxiety symptoms meant increased connections between the amygdala and other brain regions: the ventromedial prefrontral cortex, associated with fear-based and social aspects of decision making, and the subgenual anterior cingulate cortex, thought to regulate diffuse brain areas, especially those needed for processing sadness.

These findings paint a picture of connections to the amygdala as a driving factor behind negative symptoms in both PTSD and depression, with depression symptoms reflecting reduced connections and anxiety symptoms reflecting increased connections. Treatments might be improved, the researchers say, by targeting these brain networks for different symptoms and continuing to study overlap between PTSD and major depressive disorder. The researchers note that future work should explore whether these findings reflect long-lasting traits of people with PTSD and depression, rather than temporary moods brought on by their conditions.

Read the paper.