The study aims to characterize the rhythmic parameters of unipolar depressed patients that are associated with the response to antidepressants after 6 weeks of treatment.

Patients are included at the time of their hospitalization in the psychiatry unit. They perform rhythmic parameters recording within 48hours after the initiation of the antidepressant treatment. An evaluation of the evaluation of the severity of depression symptoms is performed at 2, 4 and 6 weeks after the initiation of the antidepressant treatment.

A correlation analysis will be performed with rhythmic parameters and the response to the antidepressant treatment.

Inclusion Criteria:

• current unipolar major depressive disorder according to the Diagnostic ans Statistics Manual (DSM)V
• MADRS score > 25

Exclusion Criteria:

• other psychiatric disorder
• current treatment with thymoregulating agent
• clozapine treatment
• heart disease that could alter heart rate characteristics
• disease associated with fever
• shift work within 3 months before inclusion
• transmeridian travel in the preceding month
• guardianship