Resolution of delusional depression after recovery from delirium

Little attention has been given to the effects of delirium on the course of depression. In clinical practice, we sometimes observe delirium brought on incidentally by severe physical illness or therapeutic drugs such as tricyclic antidepressants. Recently, investigators have discussed whether delirium can in fact have a beneficial effect on the course of depression. We present three cases of delusional depression in which depressive symptoms resolved after patients recovered from incidental delirium caused in two cases by medication, and by respiratory distress leading to asphyxiation in the third. We surmise that delirium may create a biological effect similar to that of electroconvulsive therapy (ECT), which is widely hailed as an effective treatment for delusional depression. Retrograde amnesia caused by delirium and the supportive milieu during treatment of the delirium may have a beneficial psychological effect on recovery from delusional depression.