Freud’s Mourning and Melancholia distinguishes between the two on the basis of self-knowledge. Melancholia is related to an “object loss which is lost from consciousness”– the melancholic might know rationally what they have lost, but not what specifically was lost to them. In mourning, there is “nothing about the loss which is unconscious” (245). In mourning, the world becomes empty and meaningless; in melancholy, the ego does. Finally, the melancholic does not confine this feeling to the present, but stretches it to the past: things were never any better, and (assumedly) they will never get any better.
Their complaints are “not plaints in the old sense of the word” (248)– plaint meaning wail or cry– because they are not sufficiently humble, and they are really speaking about someone else through themselves (i.e. the wife who claims she is incapable is actually accusing her husband of being incapable). This is a massively unsympathetic thing to say. It’s especially interesting given that earlier in the essay, Freud seems to take pains to understand the melancholic’s attitude at face value: if someone expresses they are in pain, even if we can’t see that pain, he argues that it is real because it is real to them. (This reminds me of Amy Hollywood’s breakdown of the real and the true with respect to religious melancholy– just because something isn’t real for us doesn’t mean it’s not real for the person experiencing it.) But here, he seems to reverse and say that because their frustration is actually directed at someone else, they don’t deserve sympathy.
Freud is interested in why the disease seems to alleviate in the evening, and determines that there must be a somatic reason and maybe even a somatic version of melancholy that results from “toxins”. His simultaneous consideration of the medical aspects of melancholy and at the same time his unwillingness to explore whether his psychogenic concept of melancholy can have a medical basis is confusing. There seems to be no way that medical and emotional/social/psychological melancholy can be the same thing; one is brought on by the loss of an object in which too much of the ego was invested, the other by “toxins”.
Ultimately, the awareness of the lost object is not the central factor in melancholy’s development; the most important thing is that it needs to have an ambivalent connection to that object which the ego, in trying to destroy, has turned back onto itself. The ego destroying itself is (to Freud) the most important factor of melancholy, and the one that distinguishes it from mourning. Interestingly, where I had remembered misplaced and/or temporally inappropriate mourning constituting melancholy, it is actually any situation where the ego attacks itself in place of something else that Freud believes constitutes melancholy over everything else. Failing to properly separate from an object, whether because of unawareness of it or some other reason, is what leads the ego to ambivalence, making it attack itself and resulting in melancholy.