An implantable electroacupuncture device (IEAD) treats mental illness through application of stimulation pulses applied at a specified tissue location, including at least one of acupoints GV20 and EXHN3, or their underlying nerves. In one embodiment, the IEAD comprises an implantable, coin-sized, self-contained, leadless electroacupuncture device having at least two electrodes attached to an outside surface of its housing. The device generates stimulation pulses in accordance with a specified stimulation regimen. Power management circuitry within the device allows a primary battery, having a high internal impedance, to be used to power the device. The stimulation regimen generates stimulation pulses during a stimulation session of duration T3 minutes applied every T4 minutes. The duty cycle, or ratio T3/T4 is very low, no greater than 0.05. The low duty cycle and careful power management allow the IEAD to perform its intended function for several years.