Stimulating personality: ethical criteria for deep brain stimulation in psychiatric patients and for enhancement purposes.

Within the recent development of brain-machine-interfaces deep brain stimulation (DBS) has become one of the most promising approaches for neuromodulation. After its introduction more than 20 years ago, it has in clinical routine become a successful tool for treating neurological disorders like Parkinson's disease, essential tremor and dystonia. Recent evidence also demonstrates efficacy in improving emotional and cognitive processing in obsessive-compulsive disorder and major depression, thus allowing new treatment options for treatment refractory psychiatric diseases, and even indicating future potential to enhance functioning in healthy subjects. We demonstrate here that DBS is neither intrinsically unethical for psychiatric indications nor for enhancement purposes. To gain normative orientation, the concept of "personality" is not useful--even if a naturalistic notion is employed. As an alternative, the common and widely accepted bioethical criteria of beneficence, non-maleficence, and autonomy allow a clinically applicable, highly differentiated context- and case-sensitive approach. Based on these criteria, an ethical analysis of empirical evidence from both DBS in movement disorders and DBS in psychiatric disease reveals that wide-spread use of DBS for psychiatric indications is currently not legitimated and that the basis for enhancement purposes is even more questionable. Nevertheless, both applications might serve as ethically legitimate, promising purposes in the future.