Disrupted White Matter Microstructure and Mood Disorders after Traumatic Brain Injury.

Traumatic brain injury (TBI) is associated with an elevated frequency of mood disorders that may, in part, be explained by changes in white-matter microstructure. This study is the first to examine the relationship between mood disorders and white-matter pathology in a sample of patients with mild to severe TBI using a standardized psychiatric interview. This study reports on a sub-sample of 29 individuals recruited from a large prospective study that examined the evolution of psychiatric disorders following complicated, mild to severe TBI. Individuals with TBI were also compared with 23 healthy control participants. Individuals were invited to complete the Structured Clinical Interview for DSM-IV Disorders (SCID) to diagnose psychiatric disorders. Participants who developed a mood disorder within the first 3 years were categorized into a TBI-Mood group. Diffusion tensor tractography assessed white matter microstructure using atlas-based tract-averaged and along-tract approaches. Fractional anisotropy (FA) was used as the measure of white-matter microstructure. TBI participants with and without a mood disorder did not differ in regard to injury severity and other background factors. Nevertheless, TBI participants diagnosed with a mood disorder displayed significantly lower tract-averaged FA values for the right arcuate fasciculus (p = 0.011), right inferior longitudinal fasciculus (p = 0.009), and anterior segments I (p = 0.0004) and II (p = 0.007) of the corpus callosum, as well as the left (p = 0.014) and right (p = 0.015) fronto-occipital longitudinal fasciculi. The pattern of white matter disruption identified in the current study provides further support for a neurobiological basis of post-TBI mood disorders. Greater understanding of individuals' underlying neuropathology may enable better characterization and prediction of mood disorders. Integration of neuropathology may also inform the potential efficacy of pharmacological and psychological interventions.