Every time an external force severely injures the brain – whether through a car accident, fall, war injury, or sports trauma – it leaves a lasting impact. For people with traumatic brain injury (TBI), one of the leading causes of death and injury worldwide, depression is a common symptom, occurring in half of all patients. A new study has identified brain patterns specific to TBI patients with depression that could help in tailoring personalized treatments.
While behavioral studies have linked TBI and depression, very little research to date has focused on teasing apart the symptoms at a neural level. “This study adds a strong biological element to the clinical picture,” says Daniel Krawcyzk of the University of Texas at Dallas, the senior author on the new paper just published in Frontiers in Neurology Neurotrauma.
Led by Kihwan Han, the research team wanted to identify patterns of altered amygdala neural circuitry in individuals with chronic TBI who also had depressive symptoms. They analyzed fMRI resting-state patterns in 54 individuals with chronic TBI, with an average of 8 years since their injuries; 31 of the individuals had mild-to-severe depressive symptoms and 23 individuals had minimal depressive symptoms. The researchers then compared amygdala connectivity of these TBI sub-groups. They found that “amygdala connectivity may be a potentially effective neuroimaging biomarker for comorbid depressive symptoms in chronic TBI,” they wrote.
“This is a new way to look at depressive symptoms in relation to the brain,” Krawczyk says. “Most TBI studies use surveys and questionnaire data to access this aspect of patients’ lives.”
CNS spoke with Krawczyk and Han to learn more about the study and how it is informing, and will continue to inform, brain-training strategies for people experiencing TBI.
CNS: Why do you study TBI?
Krawczyk and Han: TBI is an important issue in our society for example, both for returning wounded-warriors adjusting to ‘normal’ lives and safety for kids playing football. There have been challenges in identifying and characterizing TBI, such as difficulties in diagnosing ‘mild’ injuries and heterogeneity of injuries. Through our research, we want to contribute to proper diagnosis and treatment of individuals with TBI by overcoming these challenges to make our society better.
CNS: What have we known previously about the relationship between depression and TBI?
Krawczyk and Han: Depression is one of the most common psychiatric conditions occurring among individuals with TBI. There are significant effects of depression on individuals with TBI such as poorer cognitive function, reduced functional disability, increased suicide attempts, greater sexual dysfunction, less social and recreational activity, and poorer recovery.
CNS: What were your most excited to find? Were any findings surprising?
Krawczyk and Han: One of the most exciting findings in our paper is that the patterns of amygdala connectivity within the TBI with depressive symptoms group were specific to subtypes depressive symptoms – “cognitive” and “affective.” The cognitive factor of depressive symptoms includes items regarding: sadness, pessimism, past failure, guilty feelings, punishment feelings, self-dislike, self-criticalness, suicidal ideation, and worthlessness. The affective factor includes the items: probing loss of pleasure, crying, loss of interest, and indecisiveness.
CNS: How does this work fit in with related past work on TBI?
Krawczyk and Han: Two separate lines of research in (1) TBI without depression and (2) depression without TBI have both demonstrated marked network dysfunction of those individuals. And previous neuroimaging studies in comorbid depression among individuals with TBI have been limited to regional assessments of brain structure and function. In this context, our work is the first connectivity-based study in TBI with comorbid depressive symptoms and demonstrates strong potential for further use of this method.
CNS: What types of cognitive training is your center doing now for people with TBI?
Krawczyk and Han: We have been working on cognitive interventions that emphasize building top-down control. This typically means teaching people strategies and methods that allow them to enhance their attention, planning, and ability to focus on relevant information. We have been evaluating the Strategic Memory Advanced Reasoning Training (SMART) for people with TBI. The SMART program is a strategy-based reasoning program to improve the ability to abstract core meaning from complex information and incorporate these strategies to daily tasks. It was developed by our colleague Sandra Chapman.
CNS: What types of cognitive training do you envision in the future for TBI patients? How does this latest study inform that?
Krawczyk and Han: We envision a greater focus on individualized training for TBI patients. TBI is heterogeneous, meaning that every injury is different and so are the individual needs of different people. So, it is critical to create an individualized training, targeting specific deficits. Our study demonstrates whether a TBI individual has depressive symptoms and which types of depressive symptoms the individual has in an objective fashion. We hope that our findings in this study may help clinicians create more individualized treatment plans that more specifically target different sub-types of depressive symptoms that an individual is experiencing.
We are also very interested in the potential for using game-based simulation tools to augment top-down training. In this work, we have been investigating practical everyday life skills such as cooking or money management; these can be tested and practiced in virtual environments that allow a lot of experimental control.
CNS: What does this work mean for people with depression but not TBI? How might this week ultimately help those people?
Krawczyk and Han: Depression is a complex phenomenon. At the present time, our study does not very directly translate to the other types of clinical level depression that individuals face. In the broader sense, more work will need to be done across a range of people with depressive symptoms to better assess depression and link it to neural systems.
CNS: What is the takeaway message you most want people to understand about this work?
Krawczyk and Han: Symptoms of depression and cognitive complaints after TBI often overlap, thus it is hard to tease apart depressive symptoms from TBI. Our work may enable us to distinguish depressive symptoms from TBI-related symptoms and to classify sub-types of depressive symptoms among TBI individuals in a more objective way.
CNS: What’s next for you with this work?
Krawczyk and Han: In the future, we would like to assess if and how altered amygdala connectivity in chronic TBI with comorbid depressive symptoms may be reorganized following rehabilitation.
-Lisa M.P. Munoz
Learn more about the study of the University of Texas, Dallas, press release.