Extracting Apathy From Depression Syndrome in Traumatic Brain Injury by Using a Clustering Method

Depression and apathy are common after traumatic brain injury (TBI), and different intervention strategies are recommended for each. However, a differential diagnosis can be difficult in clinical settings, especially given that apathy is considered to be a symptom of depression. In this study, the investigators aimed to isolate apathy from depression among patients with TBI and to examine whether apathy is exclusively associated with the amount of daily activity, as previously reported in the literature.Eighty-eight patients with chronic TBI completed the Japanese versions of the 21-item Beck Depression Inventory-II (BDI-II) and the Starkstein Apathy Scale (AS). Daily activity was measured with a 24-hour life log. A hierarchical cluster analysis was applied to divide the BDI-II data into separable components, and components' correlations with results of the AS and 24-hour life log scale were evaluated.The BDI-II and AS revealed that 37 patients (42.0%) had both depression and apathy. BDI-II data were classified into four separate clusters (somatic symptoms, loss of self-worth, affective symptoms, and apathy symptoms). Loss of self-worth and apathy symptoms subscores were significantly positively correlated with total AS score (r=0.32, p=0.002, and r=0.52, p<0.001, respectively). The apathy symptoms subscore was significantly correlated with the amount of daily activity (r=-0.29, p=0.009).The findings suggest that the BDI-II can differentiate between apathy and depression among patients with TBI, which is essential when selecting intervention options. Moreover, apathy symptoms predicted patients' real-life daily activity.