Dominance of the 'nondominant' hemisphere in depression.

We examined 36 patients with major depression diagnosed by DSM-III-R to find and qualify disturbances in brain oxygenation and hemodynamics during a psychological task. A group of 36 age- and sex-matched healthy volunteers were monitored as controls. Multichannel near-IR spectrophotometry (NIRS) was used to observe real-time alterations in the oxygenation in corresponding areas of the hemispheres at the forehead during the mirror drawing task (MDT). Nearly half of the patients (12 of 24 males and 4 of 12 females) showed a 'nondominant hemisphere response pattern', which was never observed in normal volunteers during the MDT. The other half of the patients showed a 'bilateral response pattern'. There was no 'dominant hemisphere response pattern', the pattern observed in most normal males. When re-examined after recovery from depression, the response pattern of the two patients who had shown the 'nondominant hemisphere response pattern' during the course of the illness had changed to the 'bilateral response pattern'. The response pattern of the three patients with refractory depression who first showed the 'bilateral response pattern' changed to the 'nondominant response pattern' after several months. The nominally 'nondominant' hemisphere may become dominant during the course of depression.