In business, empowerment helps drive productivity. In politics, felt enfranchisement does similar, and prevents social unrest. My view is that these are the same dynamic in different areas of life. A similar dynamic plays itself out in health, economic well-being, moral life, etc., and my claim is that in each case the lack of a felt ability to effectively act produces something like depression.
The human being, as fundamentally a reflective agent in the world, must experience its own agency in the world. The alternative is for the person to give up on his own agency. This is felt as the death of responsiveness or feeling. It is a loss of hope for one's ability to live in the world. One no longer feels, because one feels consigned to thinghood rather than agency. One sees oneself as a mere object, unable to effectively respond, and thus becomes ever more like a thing, something which does not respond because it is unresponsive.
Yet some feeling always remains. As an agent, one remains responsive to one's being as an agent and the demand for action in the world is unavoidable. Acting as a thing, then, in its contradictoriness--one acts as what deos not act--is painful, even while it serves to protect one from the failure of ineffectual action. Stoicism and depression depression are aligned, if not identical. Stoicism advocates not caring about the outcome of one's actions, and yet one's actions are oneself in the world--one's placing of oneself into the world in concrete form. Empowerment thus encourages employees to take pride in their work because it allows them to see themselves in their work without pain. Empowerment is a response to the alienation from the products of one's labor which Marx critiqued. Stoicism, on the other hand, advocates self-alienation from one's actions.
Thus far, my analysis has been how the deprivation of agency moves toward depression. The same movement may be noted in reverse, however. Acting, and finding ways to effectively act, provides an antidote to depression. Acting towards a future opens up possible futures in which one may live, thus providing hope. Acting requires one to respond to something.
There are, however, two kinds of action possible. One may act towards life or towards death. One may act productively or destructively. Destructive action is an imposition on oneself which temporarily mitigates the loss of feeling, yet leaves one unaffected in the long term, leaves no real mark on the world one lives in. Productive action is action with a result one is glad to see oneself in. Destructive action is action which gives one a fleeting glimpse of the ability of action to effect things, yet does not produce such a change as one can identify with. Destructive action is action which embraces one's thinghood, that is, one's death.
Action which successfully places one--expresses one--in the world, in such a way that one can recognize oneself there, combats depression in whatever sphere that action takes place. Given that an agent is not seamlessly divisible, both depression and non-depression tend to spread, depending on what areas one takes to be important, or more relevant to one's agency.
Much of this could be construed as ad hoc rationalization of features we already knew, but the purpose of philosophical analysis of such things as depressions seems to me to lie more in placing the features in a coherent whole with respect to the rest of the world of experience for the person who experiences or otherwise has to deal with those things. We may know that getting up and doing things is helpful for those with depression recovering, but what this analysis gives is an internal view on depression which makes sense of this. Further, this analysis connects depression to other features of life and thought in ways I, at least, find interesting (the connections with Marx and felt enfranchisement).