According to the British National Institute for Health and Care Excellence (NICE), the evidence on<unk>  for depression raises no major safety concerns. As of 2017, at stimulation up to 60 min and up to 4 mA over two weeks, adverse effects include skin irritation, a phosphene at the start of stimulation, nausea, headache, dizziness, and itching under the electrode. Typical treatment sessions lasting for about 20–30 minutes repeated daily for several weeks in the treatment of depression. Adverse effects of long term treatment were not known as of 2017. Nausea most commonly occurs when the electrodes are placed above the mastoid for stimulation of the vestibular system. A phosphene is a brief flash of light that can occur if an electrode is placed near the eye. People susceptible to seizures, such as people with epilepsy should not receive<unk> . Studies have been completed to determine the<unk>  density at which overt brain damage occurs in rats. It was found that in cathodal stimulation, a<unk>  density of 142.9 A/m2 delivering a charge density of 52400 C/m2 or higher caused a brain lesion in the rat. This is over two orders of magnitude higher than protocols that were in use as of 2009.
Transcranial direct-current stimulation
Transcranial magnetic stimulation
Non-invasive cerebellar stimulation
Transcranial random noise stimulation
Thalamic stimulator
Electrical brain stimulation
Electric acoustic stimulation
Cranial electrotherapy stimulation