Assessing Approach Motivation in Depressed Individuals with a History of Concussion

Depression is the leading cause of disability worldwide. Anhedonia, a core symptom of depression, has been described as a lack of pleasure or interest, though it is a much more complex process than simply lack of pleasure. Anhedonia is made up of anticipation, motivation, enjoyment, and learning related to rewards. When an individual's motivation is impaired, reward perception is blunted as the drive to work for it is reduced. This "approach motivation" is generally subserved by the ventral striatum and orbitofrontal cortex, two areas which can be affected in a variety of neurologic conditions, including traumatic brain injury, as these subcortical structures can be affected by pathophysiological sequalae of trauma. To explore this concept, we examined data from a large ongoing study of adult depression (Dallas 2K). A total of 110 participants with depression with (n=40) and without a history (n=70) of self-reported concussion were tested on a measure of approach motivation, the Energy Expenditure for Rewards Task (EEfRT). We also analyzed depression symptom severity and the relationship between anhedonia severity to approach motivation on the EEfRT. Results revealed no significant differences between depressed adults with and without a history of concussion on approach motivation. Exploratory analyses revealed differences between high and low depression severity groups, such that high depression severity participants were less likely to select low probability/high reward tasks, but this was irrespective of concussion history. Though the main study results were nonsignificant, exploratory analyses present an opportunity for future direction of studies related to approach motivation and cognition in co-morbid depression and concussion.