LivaNova has enrolled the first patient in a multi-center trial of its vagus nerve stimulation (VNS) therapy for treatment-resistant depression.

The trial will assess whether VNS therapy is more effective than no stimulation in reducing the severity of depression symptoms. The study will involve up to 500 unipolar and 500 bipolar depression patients at as many as 100 sites across the U.S.

In September, the FDA cleared LivaNova’s Symmetry VNS therapy system for adjunctive long-term treatment of chronic or recurrent depression in patients 18 and older who are experiencing a major depressive episode and haven’t had an adequate response to four or more antidepressant treatments.