Depression is a general term of a broad syndrome with various clinical symptoms such as depressive mood, diminished interest, agitation, insomnia, and decreased appetite. Although dysregulation of hypothalamus-pituitary-adrenal system and abnormality of monoaminergic neuron have been pointed out since 1950', it has not yet reached a conclusion whether it is a cause of depression, a result of depression, or an accompanied change of depression even today. In this article, present findings for the pathophysiology of depression are reviewed from a wide viewpoint including animal model studies, genetic studies, neuroendocrinological studies, neurochemical and molecular biological studies and brain imaging studies.
