Prefrontal asymmetry in depression? The long-term effect of unilateral brain lesions

The proposal that a functional asymmetry in prefrontal cortex (PFC) may play a role in the pathophysiology of depression has sparked vigorous debate and investigation. One particularly contentious issue of clinical and theoretical importance is whether left PFC lesions are associated with the development of depression, and whether any such lesion-depression association is stable over time. To address this issue, we assessed the long-term depressive symptomotology of Vietnam veterans who had acquired left PFC lesions (n=21), right PFC lesions (n=18), non-PFC lesions (n=38), or no brain lesions (n=31) during the Vietnam War. Depressive symptoms were assessed at two different timepoints, approximately 15 and 35 years after lesion onset, respectively. There was no significant effect of PFC lesion laterality on overall depression severity at either timepoint. These data converge with previous stroke studies to suggest that PFC lesion laterality has no long-term systematic effect on vulnerability to depression.