Biological theories of depressions: premisses - and progress?

Although less undisputed in biological psychiatry than formerly, there are basically still two premisses which underly most hypotheses in biological depression research. These are deeply rooted in the medical way of thinking and have guided the construction of DSM-III. The first is that depressive symptoms and complaints cluster in one or more discrete syndromes, and the second is that these correspond to separate nosological entities, characterized by specific biological derangements and pathogenetic processes. Below a number of issues are raised which cast doubts on the validity of these premisses and on the progress made in pinpointing the derangements looked for.