Revisiting the concept of bipolar depression: comparison of diagnostic validators between melancholic and non-melancholic episodes

The current definition of bipolar disorder derives with minimal changes from one that emerged through expert consensus in the late 1970s, and the topic of its validity tended to be neglected in the literature. The aim of this exploratory study was to compare patients with bipolar disorder with a history of melancholic and non-melancholic depressive episodes in a series of external diagnostic validators. One hundred eight subjects were categorized as melancholic or non-melancholic in relation to their history of depressive episodes through the clinician-rated Sydney Melancholia Prototype Index (SMPI). The external validators used were clinical-demographic variables, family history of bipolar disorder, neurocognitive performance and functional outcome. There were 43.5% of the patients with a history of melancholia and 56.5% of non-melancholic depression. Non-melancholic depressions were overrepresented in females, while melancholic depressions had a female:male ratio closer to unity. Patients with melancholia had more history of BD in first-degree relatives and better functional outcome than those with non-melancholic depression. There were no differences between groups regarding neurocognitive performance. Results tended to be unchanged when controlled for confounders. Our preliminary results highlight the inherent heterogeneity in the current concept of bipolar depression, and suggest the need for further clinical research to elucidate its validity.