Major Depressive Disorder (MDD) is found throughout the spectrum of a Traumatic Brain Injury (TBI). Cognition, psychosocial function, social roles, and functional outcomes (Hibbard, Ashman, Spielman, Chun, Charatz, & Melvin. 2004) are commonly negatively affected by depression after TBI. The article theorizes that "as persons with TBI improve functionally, they become more self-aware, and depression ensues as they struggle to accept the outcome of a life altering event.".
The study chose its participants from a pool of 1279 potential participants and narrowed it down to 471, who fit the inclusion criteria. The inclusion criteria for the experiment included age at injury being between 14 to 65 years and the subject participated in a structured phone interview, during which a Beck Depression Inventory-II (BDI-II) was completed. Nineteen percent of the group had clinically significant symptoms of depression according to the BDI-II test performed. The subjects were then divided by TBI severity and accessed. The subjects with a mild injury were defined as those with a Glasgow Coma Scale (GCS) of 13 to 15, meaning they had higher functions. Subjects classified as suffering from a moderate to severe TBI have a GCS of less than 13. Twelve percent of the mild subjects and one percent of the moderate-severe subjects had clinically significant depression. The study concluded that a moderate correlation was found between FSE and BDI-II, where worsening depressive symptoms correlated with worsening functional outcomes. The results lead to two different predictive models; both containing GCS but different variables. The researchers encourage further studies and monitoring of depressive symptoms. .
The researchers created a theory based on a cause and effect. They used a longitudinal method of research to conduct their experiment, meaning they conduct observations of the same subjects over a period of time, unlike a cross-sectional method, where subjects are observed but only at one point in time.