The heterogeneity of the depressive syndrome: when numbers get serious

The current criteria for major depression (1) have been criticized for the heterogeneity of the clinical syndrome they define. This has led to suggestions of alternative classifications, most recently by G. Parker in this journal (2). According to the critics, the polymorphic syndrome is partly to blame for the fact that the treatment of depression still has not moved beyond the trial and error approach and that the genetics and neurobiology underlying the depressive disorder still remain largely unknown and without practical significance (3). Two of the most interesting studies on major depression, conducted within recent years, reflect this problem: