[Near-infrared spectroscopy in psychiatry]

Near-infrared spectroscopy (NIRS) is a noninvasive optical method for in vivo measurement of regional brain tissue oxygenation. Light from the near-infrared spectrum can penetrate the skull and is mainly absorbed by oxyhaemoglobin (O(2)Hb) and desoxyhaemoglobin (HHb). From the amount of reflected near-infrared light in relation to the amount absorbed by brain tissue, regional changes in O(2)Hb and HHb concentrations can be calculated spectrophotometrically. It has been shown that NIRS is not only able to measure massive disturbances in cerebral blood circulation due to serious neurological diseases, but that it also is sensitive enough to assess task-specific patterns of activation in healthy subjects during circumscribed cognitive processes. Preliminary investigations indicate altered regional brain tissue oxygenation in psychiatric patients during cognitive activation tasks. The NIRS outmatches other functional imaging methods in that it has no side effects and is well tolerated by psychiatric patients. Furthermore, it can be applied quickly and easily. Thus, NIRS is a potential screening method in psychiatric settings, provided that robust parameters of reliable diagnostic and/or prognostic value can be developed for individual psychiatric illnesses. However, this will depend on broader application of the method combined with established neurophysiological procedures and functional imaging techniques in psychiatric research.