Resistant Depression and Vagus Nerve Stimulation : a Medico-economic, Multicenter, Randomized and Open Trial

Depression is a common illness, affecting 17% of the population over the course of a lifetime. A third of depressions relapses and progresses to recurrence and resistance to treatments. Despite the optimization of antidepressant medical strategies, 20 to 40% of depressions do not respond to treatment. This is particularly worrying as 6% of non-responder patients will die by committing suicide. The term treatment-resistant depression (TRD) is used when two or more (and often many more) well conducted antidepressant treatments from different classes have failed to achieve remission.

Depression has a major impact on quality of life, socio-professional functioning and healthcare consumption. According to the World Health Organization (WHO), depression will be the second cause of healthcare costs in the world by 2020. RD alone accounts for 30 to 40% of the annual cost of depression.

Sometimes, TRD is part of a bipolar illness, a psychiatric condition characterized by the alternation of depressive and maniac episodes that affects 4% of the population. In this case, the challenge is even bigger because (1) antidepressants are no well tolerated, further reducing the therapeutic options in case of resistance, (2) the severity and duration of the depressive episodes are the main factors explaining the deterioration of the quality of life and the increasing cost of cares for these patients. Bipolar RD currently accounts for 20% of all psychiatric spending.

The standard treatment for TRD is electroconvulsive therapy (ECT), which results in a response in 60 to 70% of cases after a few weeks of treatment. However, the improvement is often transient and 40% of patients relapse within 6 months of the initial ECT session. Moreover, ECT is often not well tolerated because of the frequency and the intensity of the memory disorders associated, the repetition of anesthesia and hospitalizations and its social stigma. Refusals and requests to stop ECT are therefore common even when it is effective, as these constraints are sometimes experienced as being unbearable in the long-term. This therapeutic impasse therefore makes TRD a priority public health target to which it is urgent to provide a realistic medico-economical response.

The literature suggests that Vagus Nerve Stimulation (VNS) has unique kinetics of efficacy in depression, particularly in preventing the long-term recurrences, and therefore responding to the lack of effective maintenance treatment in TRD. In fact, the benefits of VNS gradually accumulate over 12-24 months, which makes it complementary to more incisive treatments like ECT. Finally, its efficacy-tolerance profile appears to be similar in uni and bipolar TRD, giving VNS a potentially unique place in the therapeutic arsenal in psychiatry. VNS has been approved for over 15 years as a treatment for RD in the Unites States and Great-Britain.