robtex said:
how many kinds of depression exist and what are the speculated causes?
Kinds of depression? I suppose there could be as many kinds as sufferers. If we could identify antecedents, biological markers and the like then maybe a change of scene and a tailored pill would cure it.
A characteristic of depression is that it is cyclic in many cases. It seems to dissipate as cyclically as its onset in a repeated pattern. Other people have a major depressive episode and no more problems. Social anxiety is a risk marker for depression. All this boils down to a spectrum of disorder, no matter how you label it.
Exercise has been shown to be just as effective as drugs in warding off depressive episodes. But in cyclic cases, the effectiveness of treatments needs to judged in relation to quality of life improvements during depressive episodes and also in relation to duration where the problem can dissipate in the absence of any therapy.
A change of context is a powerful tool in changing psychological and physiological symptoms. Netdoc may be onto something.