From Conversations with C. G. Jung
The unconscious can also express itself through a depression.
People so spoilt by success that they are no longer accustomed to struggle for it, must sometimes suffer disaster in order to wake up: otherwise life is too easy for them.
They are too comfortable and they have to pay for it somehow.
Many are plagued by chronic ailments or intermittent depressions because fate does not torment them in other ways.
Chronic illness or depression is then directly meaningful. They are mechanisms, to be sure, but so long as people are enslaved by these mechanisms they are saved from a more cruel fate.
There are some patients the analyst must even treat emotionally, and he must not allow certain other patients to exploit him. He can talk very openly and sternly to these and even respond emotionally to them. Such people enslave others.
They must be shown that they have a desire to dominate: they must be told the truth.
People of this kind are subject to depression because they want to rule others but cannot manage to. ~Carl Jung, Jung-Ostrowski, Page 15.