Depression, locus of control, and the effects of epilepsy surgery.

The purposes of this investigation were (a) to determine the relationship between interictal depression and a potential psychosocial risk factor (locus of control), (b) to examine changes in self-reported depression after anterior temporal lobectomy (ATL), and (c) relate postoperative changes in depression to alterations in surgical outcome and locus of control. Thirty-seven patients with intractable seizures of temporal lobe origin were administered measures of depression and locus of control both preoperatively and 6 months postoperatively. Results revealed a significant preoperative relationship between depression and an external locus of control, but this relationship no longer existed postoperatively. Postoperative declines in depression were independent of any alterations in locus of control. Further analyses revealed that depression declined significantly only in patients rendered completely seizure-free by ATL, whereas patients who were significantly improved (greater than or equal to 75% reduction in seizure frequency) but continued to experience some seizure activity showed no changes in self-reported depression. Finally, a wide variety of neurologic and seizure-related variables were shown to be unrelated to depression. The clinical and theoretical significance of these findings is discussed.