Effects of Left and Bilateral Transcutaneous Auricular Vagus Nerve Stimulation on Pain, Mood, and Autonomic Function in Female Fibromyalgia Patients

taVNS was performed using the Vagustim device (Vagustim Health Technologies, Teknokent, Istanbul, Türkiye) at the tragus and concha regions for 30 minutes, with a frequency of 25 Hz and a pulse width of 300 µs in both groups. The difference in stimulation between the groups depends only on to which ear it was applied. Electrical stimulation was increased in 0.1 mA steps until the detection threshold was reached.