It says a lot. If the body can fix this supposed chemical imbalance, then why use drugs which could have other long-term health detriments?
Also, your presuming that the chemical imbalance causes depression, as oppossed to the possibility that negative self-thought/behaviour stimulates this imbalance which perpetuates the problem. The chemical's released simply become a symptom. As I openly posted above, this is simply an opinion I formed based on sources I read. I could be wrong, I'm not a med student. But I could also be correct; It appears the medical community as a whole is not even sure. It will be interesting to see Kfunk on this one.
I don't know many people who have had true clinical depression, but those that have did not have any social "cause" for it, or overlying "feelings of worthlessness", that prompted the condition. Admittedly this is an argument from anecdote, but I believe it's specious reasoning to argue that depression is caused by a cognitive dissonance between expectations and "social conditioning", when there are clear and coherent biological hypotheses for the genesis of the chemical imbalances of the condition.
On chemicals and causation
An important point that seems to be missed here is that 'chemical imbalances' and 'negative self-thought' may either be intimately related, or may be one in the same thing.
If we accept the neurochemical basis of the human mind then doesn't it seem reasonable that chemical imbalances could alter one's temperament, thought processes, mood, and so forth, and similarly that one's experiences and thought processes may alter brain chemistry and structure. Evidence exists for both. We
know that drugs (read: chemicals) can alter cognition, experience and behavior. For a current hot example of the link between genes, chemicals and behavior see the role of
Monoamine Oxidase in Aggression. Furthermore, we
know that experiences can alter brain structure and cognition - for example see studies on hippocampal volume in
taxi drivers and one of many thousands of studies
linking early childhood relationships with later emotional functioning.
It may well be, and indeed seems likely, that
both nature (life experiences, exposure to chemicals and disease) and nurture (genes, inherent brain chemistry) cause depression. It may well be that one is born with a predisposition on account of the genes that control brain chemistry, determining things like temperament (upbeat? anxious? risk-taking?) and propensity towards certain thought patterns, and that such tendencies interact with experience to determine whether one becomes depressed. Things are complicated when we realise that environmental influences (even in the womb!) - social, chemical, infectious etc -
can alter gene expression in cells.
tl;dr -->
Essentially the picture is complicated. Brain chemistry alters cognition/behavior and hence experience. Experience alters brain chemistry. In many cases chemical and mental changes are one in the same thing, though I expect it is more likely that they simply overlap in a lot of cases (given that specific neurotransmitters and chemical processes each seem to subserve multiple mental functions).
My opinion is that, considered broadly, you cannot, and should not, try to fully separate the chemical and the mental/social/whatever. There may, of course, well be instances of depression which are primarily chemical (e.g. where ultimately a gene is at fault) or primarily reactive (e.g. depression triggered by loss). Regardless, we need to appreciate the complex interelationships that exist.