Anxio-depressive disorders are characterized by a difficulty in regulating the negative or aversive emotions adequately. These dysfunctions have been linked to a deficit in prefrontal cortex activity. The latter has an inhibitory influence on limbic regions -especially the amygdala- involved in the generation of emotions. By this means, the prefrontal cortex intervenes in the control of the sympathetic and parasympathetic branches of the autonomic nervous system whp are responsible for the physiological components of the emotion, including the variations of the cardiac rhythm (HRV: heart rate variability).

In emotionally demanding situations, the activity of the prefrontal cortex is generally associated with an increase in parasympathetic activity that is exerted by stimulation of the vagus nerve. In patients with anxio-depressive disorder, there is a decrease in the activity of the autonomic nervous system whose variability in heart rate is a recognized marker.

Many studies show a beneficial impact of transcranial direct current stimulation (t-DCS) on anxio-depressive symptoms, particularly when a particular area is targeted: the dorso-lateral prefrontal cortex. The impacts of this intervention are multiple and aim in particular to modulate the activity of the autonomic nervous system to promote regulation.

Biofeedback HRV is a technique that allows you to learn how to modulate your heart rate by means of respiratory control exercises. The patient receives an immediate feedback on the effectiveness of his learning (basic principle of bio-feedback). This intervention will allow to act on the parasympathetic activity and to promote a vagal tone adequate to the emotional regulation. Numerous studies have demonstrated the favorable impact of HRV biofeedback on the reduction of anxious and depressive symptoms.

Since the vagus nerve seems to be a primary pathway in physiologically emotional regulation, and considering that vagal tone can be stimulated by both the activity of the prefrontal cortex and through respiratory control, it appears interesting to study the association of t-DCS with HRV biofeedback techniques.

The first objective of this study is to show that HRV biofeedback training coupled with t-DCS is associated with a greater decrease in anxious symptomatology. The secondary objective of the study is to show that a coupling of these two techniques is associated with an increase of the variability of the cardiac rhythm as well as a more important decrease of the depressive symptomatology.

Inclusion Criteria:

• Diagnose of anxio-depressive disorder
• Good understanding of French
• High anxiety level (STAI questionnaire score higher to 46) with reported difficulties to manage this anxiety.

Exclusion Criteria:

• Alcohol dependence (assessed by the AUDIT questionnaire)
• Pregnancy
• t-DCS contra indications : traumatic brain injury, epilepsy, known bipolar disease, electronic or metalic implant
• Known cardiac arrhythmia or intake of beta-blockers