Exactly. What I think people lose sight of is that people with chemical imbalances do, is to create all sorts of behavioral coping mechanisms in their daily lives before they ever see any type of chemical intervention. Once they get that chemical intervention, they then need to deal with the psychological and behavioral issues built up over the years of dealing with a chemical imbalance.

This isn't like a simple infection, where you take a pill and it will go away.

Yes. Psychology must be treated cybernetically, as a historical system of self-environment relationships, which produce state changes within the self.

For anyone interested in "chemical imbalance" theory, I highly recommend reading Carhart-Harris and Friston's paper "REBUS": http://pharmrev.aspetjournals.org/content/71/3/316 -- the basic gist of Friston's model is that the brain functions as a prediction engine, whose "prior probabilities" are "programmed" by past experience (within some environment). This paper addresses the role of serotonin: it reduces the "weighting" of our "prior probabilities" which gives them some malleability, meaning we can allow ourselves to adjust more fully to a new environment (or, if you flood yourself in serotonin, like with psychedelics ... it can nudge your highest-level priors, such as "who am I"?).

So from this perspective, we can see depression as a mis-adjustment between one's self (i.e. adaptation to past environments) and one's current environment (no chemicals involved here), and serotonin can provide a little nudge toward re-adapting.