A method for diagnosis of a mood disorder or predisposition therefor in a test subject is disclosed. The method includes the steps of determining binocular rivalry rate in the test subject and comparing the binocular rivalry rate with a corresponding reference rivalry rate to diagnose presence or absence of the mood disorder or predisposition therefor. Also disclosed is use of the diagnostic method in genetic linkage studies for the identification of the molecular defect(s) underlying these disorders, and for the identification of compounds which may alleviate such disorders.