A method of treating a mental disorder of a patient includes 1) generating, by an electroacupuncture device implanted beneath a skin surface of the patient at or near an acupoint corresponding to at least one of a trigeminal nerve and an occipital nerve of the patient, stimulation sessions at a duty cycle that is less than 0.05, and 2) applying, by the electroacupuncture device, the stimulation sessions to at least one of the trigeminal nerve and the occipital nerve by way a central electrode and an annular electrode located on the electroacupuncture device in accordance with the duty cycle.