Neuroendocrine aspects of mood disorders are showing a definite shift from studies that attempt to assess the responsivity of monoamine receptors, especially noradrenaline and 5-hydroxytryptamine, to studies that focus on the primary neuroendocrine stress system, namely, the hypothalamic-pituitary-adrenal axis. Recent research has helped to delineate the subtle changes that take place in this axis in depression, together with the disturbances that may result from such risk factors as maternal deprivation or sexual abuse.