HPA axis function in mood disorders

Our understanding of the neurobiology of mood disorders is advancing rapidly. Despite the initial enthusiasm for the monoamine theory of depression, it has been unable to explain the complex actions of antidepressant drugs or to provide a comprehensive explanation of the pathophysiology of the manifold biological, cognitive, and psychological symptoms of mood disorders. In recent years, attention has turned to models of mood disorders that focus on adaptations to stress. Considerable experimental and clinical evidence supports a role for hypothalamic–pituitary–adrenal (HPA) axis dysfunction in the pathogenesis of major depression and bipolar disorders.