There are a few things that should be considered as part of this discussion.
There remains some controversy regarding the nosological status of melancholia.1 For instance, there is some debate as to whether it constitutes a stand-alone category, or whether—invoking a dimensional model—melancholia represents simply a more severe type of depression.
A good discussion of these issues is provided by Gordon Parker, MD, PhD, DSc, in Psychiatric Times, January 20, 2017. With respect to melancholia as a distinct category or illness, Max Fink, MD, and Michael Alan Taylor, MD, have propounded a very specific description of a discrete disease entity, characterized by “specific behaviors, vegetative signs, and validated by neuroendocrine abnormalities (cortisolemia).”
In the discussion, I am alluding to the title of Julian Jaynes’s controversial book, The Origin of Consciousness in the Breakdown of the Bicameral Mind. In their seminal paper, Ghaemi and Dalley lay out the case for breaking down the dichotomous classification of mood disorders and for returning to a more Kraeplinian understanding of manic and depressive states. Ghaemi and Dalley first explain the difference between the Kraeplinian concept of manic-depressive illness (MDI) and our present DSM model of unipolar versus bipolar disorder. In essence2:
For bipolar disorder, the condition is defined by polarity: presence or absence of a manic episode…For MDI, the condition is defined by episodicity: recurrent mood episodes define the illness, irrespective of polarity…MDI means recurrent manic or depressive episodes. Bipolar disorder means recurrent manic and depressive episodes. These are quite different concepts.
The authors also punch some holes in the DSM category of major depressive disorder (MDD), which they argue is of “questionable” validity. My own view of MDD, as I have quipped to Dr Ghaemi, is that it is broad and vague enough to apply to a week-old ham sandwich!
1. Fink M, Taylor MA. Resurrecting melancholia. Acta Psychiatr Scand Suppl. 2007;(433):14-20
2. Ghaemi SN, Dalley S. The bipolar spectrum: conceptions and misconceptions. Aust N Z J Psychiatry. 2014;48(4):314-324.