Cranial electrotherapy stimulation (CES) is a form of neurostimulation that delivers a small, pulsed, alternating current via electrodes on the head. CES is used with the intention of treating a variety of conditions such as anxiety, depression and insomnia. CES has been suggested as a possible treatment for headaches, fibromyalgia, smoking cessation, and opiate withdrawal, but there is little evidence of effectiveness for many of these conditions and the evidence for use in acute depression is not sufficient to justify it.