Psychoanalytic theories of depression

Look up: Melancholia, Loss of the loved object

It can be a response to object loss, or the perceived threat or reverie, dream, day dream of it.

Mourning and Melancholia by Freud, PDF on archive.org

Full citation:

Freud, S. Mourning and Melancholia. Journal of Nervous and Mental Disease, 56, 543-545.

Handpicked papers by experts

Coyne, J. C. (1986). Essential papers on depression. New York: New York University Press.

Ambiguity and controversy : an introduction Notes on the psycho-analytical investigation and treatment of manic-depressive insanity and allied conditions, Karl Abraham
Mourning and melancholia, Sigmund Freud
Edward Bibring's theory of depression, David Rapaport
An intensive study of twelve cases of manic-depressive psychosis, Mabel Blake Cohen [and others]
A behavioral approach to depression, Peter M. Lewinsohn
Learned helplessness and depression, William R. Miller, Robert A. Rosellini, Martin E.P. Seligman
A self-control model of depression, Lynn P. Rehm
Maladaptive cognitive structures in depression, Maria Kovacs and Aaron T. Beck
Learned helplessness in humans : critique and reformulation, Lyn Y. Abramson, Martin E.P. Seligman, and John D. Teasdale.
Toward an interactional description of depression, James C. Coyne
Psychosocial theory and research on depression: an integrative framework and review, Andrew G. Billings and Rudolf H. Moos
Depression : a comprehensive theory, Ernest S. Becker
A three-factor causal model of depression, George W. Brown
Risk factors for depression: what do we learn from them?, Lenore Sawyer Radloff
Controversies in depression, or do clinicians know something after all?, George Winokur
Recent genetic studies of bipolar and unipolar depression, David L. Dunner
A summary of biomedical aspects of mood disorders, Ross J. Baldessarini.

Good luck on your journey!

Also interested in the psychology of grieving or mourning a loved one? Check out Essential Papers on Object Loss!