New research has identified a potential brain-based biomarker for depressive symptoms in people who have experienced a traumatic brain injury (TBI).
About half of those who experience a TBI will also experience depression within a year, according to researchers. Patients with both are more likely to have reductions in cognitive performance, greater functional disability, increased suicide attempts, and other social and sexual difficulties.
Since depression symptoms vary greatly, diagnosing the condition in those who also have a TBI is difficult, according to researchers at the Center for BrainHealth at The University of Texas at Dallas.
Published in Frontiers in Neurology Neurotrauma, the new study found that people with traumatic brain injury and depression exhibit increased brain connectivity between multiple regions and sub-networks of the brain and the amygdala, the part of the brain responsible for emotional processing.
Researchers also observed differences in brain connectivity patterns that predicted the type of depressive symptoms, specifically whether individuals leaned toward cognitive symptoms, which are related to thought patterns, or affective symptoms, which are related to general mood.
“It is very difficult to tell the difference between traumatic brain injury symptoms and depression symptoms,” said Kihwan Han, Ph.D., the study’s lead author and postdoctoral research associate at the Center for BrainHealth.
“We are hopeful that our findings that illuminate changes in amygdala connectivity patterns will become a useful tool that will help clinicians objectively diagnose subtypes of depressive symptoms in traumatic brain injury and create individualized treatment plans.”
For the study, researchers analyzed MRI scans of 54 people, between the ages of 20 and 60, who have suffered TBI, including 31 with mild to severe depressive symptoms and 23 with minimal depressive symptoms.
Researchers compared depressive symptoms using the Beck Depression Inventory-II. They also conducted neuropsychological measures. Individuals with TBI ranged from lower moderate disability to lower good recovery or five to seven points on the eight point Extended Glasgow Outcome Scale.
While all individuals in the TBI group were at least six months post-injury at the time of the study, the average length of time since injury was eight years with no history of any significant, clinically-diagnosed neurological or psychiatric disorders or history of depressive symptoms prior to their TBI. Primary causes of injury included blasts, blunt force trauma, falls, athletic impacts, and vehicle accidents.
Although those with depressive symptoms showed an overall increase between various brain regions and the amygdala, those who expressed a predominance of cognitive symptoms, such as thoughts of guilt, worthlessness, self-dislike, or suicidal ideation, demonstrated reduced amygdala connectivity with prefrontal cortices of the default mode and cognitive control networks, the study found.
Those who showed greater depressive affective symptoms, such as crying, loss of interest, indecisiveness and loss of pleasure, showed reduced amygdala connectivity with the brain regions of salience (the insula), attention (the parietal lobules), and visual networks, the imaging study found.
The new study is part of a larger research endeavor led by principal investigator Daniel Krawczyk, Ph.D., an associate professor of cognitive neuroscience and cognitive psychology at the Center for BrainHealth. The Department of Defense-funded study investigates the effects of a strategy-based cognitive training in veterans and civilians who have sustained a traumatic brain injury.
“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,” said Krawczyk. “We look forward to being able provide a more robust picture of how cognitive training may affect behavioral symptoms associated with structural brain change due to injury.”
As part of future work, Han will analyze whether such reductions in depressive and stress-related symptoms after the training are associated with changes in amygdala connectivity.