Transcranial direct current stimulation (tDCS) for depression

Six episodes of either treatment‑emergent mania or hypomania (Young Mania Rating Scale score greater than 8) were reported in a randomised controlled trial (RCT) of 120 patients treated by active transcranial direct current stimulation (tDCS) plus sertraline, active tDCS plus placebo, sham tDCS plus sertraline, or sham tDCS plus placebo. Five episodes (including 2 manic episodes) were from the active tDCS plus sertraline group and 1 was from the tDCS‑only group (no further details provided).

Skin lesions were reported in all (5/5) patients treated by 2 mA tDCS and in 1 (1/10) patient treated by 1 mA tDCS in a case series of 15 patients treated by 1 mA or 2 mA tDCS. Generally, the lesions occurred after the fourth or fifth stimulation, showed stable superficial extensions during further tDCS and healed without scars about 1–3 weeks after the end of the tDCS treatment.

A burning sensation was reported in 9% of the studies in the active tDCS group and in 10% of the studies in the sham tDCS group in a systematic review of 117 studies (p value not significant).

Skin redness 2 weeks after treatment was reported in 25% (13/60) of patients in the active tDCS group and in 8% (4/60) of patients in the sham tDCS group in the RCT of 120 patients (p=0.03). Skin redness was reported in 23% (10/42) of patients in a follow‑up study of 42 patients whose depression had responded to tDCS treatment in the RCT of 120 patients.

Itching was reported in 39% of the studies in the active tDCS group and in 33% of the studies in the sham tDCS group in the systematic review of 117 studies (p value not significant and no details of timing provided). Tingling was reported in 22% of the studies in the active tDCS group and in 18% of the studies in the sham tDCS group in the systematic review of 117 studies (p value not significant and no details of timing provided).

Headache was reported in 15% of the studies in the active tDCS group and in 16% of the studies in the sham tDCS group in the systematic review of 117 studies (p value not significant). Headache was reported in 19% (8/42) of patients in the follow‑up study of 42 patients whose depression had responded to tDCS treatment in the RCT of 120 patients.

Light‑headedness was reported in 40% of patients when tDCS was administered weekly and in 17% when tDCS was administered once every 2 weeks in a case series of 26 patients treated by tDCS for up to 6 months after an acute course of tDCS (absolute numbers not reported).

Somnolence was reported in 16% (7/42) of patients in the follow‑up study of 42 patients whose depression had responded to tDCS treatment in the RCT of 120 patients. Fatigue was reported in 10% of patients when tDCS was administered weekly in the case series of 26 patients treated by tDCS for up to 6 months after an acute course of tDCS (absolute numbers not reported).

Blurred vision was reported in 7% of patients when tDCS was administered weekly and in 11% when tDCS was administered once every 2 weeks in the case series of 26 patients treated by tDCS for up to 6 months after an acute course of tDCS (absolute numbers not reported).

Panic attacks were reported in a single case report 5 days after starting tDCS treatment. It was hypothesised that the patient, who was left‑handed and dyslexic, had right hemispheric dominance.

Nausea was reported in 10% of patients when tDCS was administered weekly and in 6% when tDCS was administered once every 2 weeks in the case series of 26 patients treated by tDCS for up to 6 months after an acute course of tDCS (absolute numbers not reported).

In addition to safety outcomes reported in the literature, specialist advisers are asked about anecdotal adverse events (events which they have heard about) and about theoretical adverse events (events which they think might possibly occur, even if they have never done so). For this procedure, specialist advisers reported induction of phosphenes ('flashing lights') with anterior stimulation positions as an anecdotal adverse event. They considered that the following were theoretical adverse events: precipitation of seizures, exacerbation of depression, interference with implanted electrical devices and twitching of facial muscles.