Previously part of the challenge to brain health experts is distinguishing the symptoms between traumatic brain injury (TBI) and depression. However, recent findings indicate that a large percentage of individuals diagnosed with TBI will also experience depression in the year after.

Using neuroimaging biomarkers between the symptoms of traumatic brain injury and depression, the study based its findings on 54 patients diagnosed with chronic TBI. This type of injury to the brain may be caused by any one factor including blasts, blunt force, traumatic fall, athletic impacts, vehicular accidents or even combinations of these injuries.

During tests, the researchers observed the amygdala's connectivity to the different regions of the brain. For the participants, who have had eight years of diagnosed traumatic brain injury, connectivity was markedly increased.

Researchers then noticed that individuals whose symptoms were mostly linked to cognitive depression displayed lower amygdala connectivity with prefrontal cortices of the default mode network and the cognitive control network. Similarly, individuals with symptoms of affective depression displayed reduced amygdala connectivity to the brain's salience networks, which regulate focus and attention.

Based on these findings, the researchers believe that increased amygdala connectivity essentially points to its potential as an effective neuroimaging biomarker for depression symptoms. Furthermore, based on the disparities in connectivity distinction between cognitive depression (relating to thought patterns) and affective depression (relating to mood and emotional patterns) may  be more easily made.

Cognitive depression symptoms are often expressed as a sense of guilt, low self-worth, dislike of the self and even suicide. Affective depression symptoms, on the other hand, manifest with tears, decreased or lack of interest, difficulty in decision-making and  loss of the sense of pleasure. 

These results, although based on a small number of subjects, have encouraged researchers sufficiently that more individualised plans for treatment may eventually be developed for those diagnosed with chronic TBI and depression.

This study is part of a larger Department of Defense-funded research, which aims to analyse the effects of strategy-based cognitive training for veterans and civilians alike who have been diagnosed with TBI. Lead investigator Daniel Krawczyk of the DoD project relates, "Our initial findings are very encouraging and reveal a pronounced decrease in depressive symptoms and reduction in stress-related symptoms in individuals with traumatic brain injury who participated in the Center for BrainHealth-developed brain training."