Lateralized auditory processing in depression: dichotic click detection.

The intensity needed to detect dichotic click stimuli was measured in 14 bipolar depressed patients, 19 unipolar depressed patients, and 15 normal controls. The results replicated, in unmedicated bipolar depressed patients, an earlier finding of reversed lateral asymmetry in medicated affective psychotic patients. Two new findings concern the relation of lateral asymmetry patterns to diagnostic subtypes of the Research Diagnostic Criteria and symptom ratings on the Schedule for Affective Disorders and Schizophrenia. First, patients with bipolar disorders (history of mania or hypomania) were more likely than patients with unipolar disorders to display reversed lateral asymmetry. Second, greater severity of depressive or endogenous symptoms was associated with less lateral asymmetry.