Insomnia and treatment-resistant depression.

Depression and sleep disturbance are related closely with bidirectional relationship. The heterogenic diagnostic criteria of major depressive disorder composed by the myriad combination of symptoms including sleep disturbance. Insomnia is an identifiable risk factor for depression and the treatment of insomnia might be able to prevent subsequent major depressive episodes which draws psychiatrists' attention to the interface of psychiatry and sleep medicine field. It is important to identify occult sleep disturbance in patients with treatment-resistant depression to improve treatment outcome. New tools to objectively measure sleep at home environment represent a great march in clinical care and research modalities but need further validation before they can be applying widespread at sleep and depression intersection. Careful evaluation and measurement of the phenotype and nature of sleep disturbance will continue to advance understanding of the biological bases of psychiatric disorders and the connections with sleep.