Although it is not completely understood why, cases of mild traumatic brain injury are more often associated with new-onset depression than those of moderate or severe traumatic brain injuries. Studies have shown that rates of depression prior to injury are associated with rates of depression after injury, but the risk factors for those who have never experienced depression prior to the injury have not previously been made clear.
In a preliminary study, researchers recently found that there were two significant indicators of new-onset depression in cases of mild traumatic brain injury. These indicators were increased age (in relation to the controls, not necessary a certain age) and the presence of a subdural lesion in the left frontal lobe. The prevalence of new-onset depression was 18% and was found up to a year after the trauma.
These two indicators could help identify high-risk individuals so that proper treatment could be administered earlier.
Rao V, Bertrand M, Rosenberg P, et al. Predictors of new-onset depression after mild traumatic brain injury. The Journal of Neuropsychiatry and Clinical Neurosciences. April 2010).