Review of: Teixeira Leffa D et al, JAMA Psychiatry 2022;79(9):847–856

Type of Study: Randomized double-blind sham-controlled trial

Does wearing a cap powered by less than 1% the juice of a nine-volt battery actually do anything? Transcranial direct current stimulation (tDCS) delivers a weak electrical charge to the scalp, and patients are increasingly using this device on their own, inspired by small but promising studies in depression. This study assessed its effects in ADHD.

The researchers randomized 64 adults with moderate to severe inattentive symptoms of ADHD to either daily tDCS or sham therapy for 28 days. The subjects stopped stimulants 30 days before the study, and none of them were taking other ADHD medications during the study. The subjects had no significant psychiatric comorbidities. Their average age was 38, and women were overrepresented in the treatment arm (60% vs 35%). The primary outcome was self-reported inattention at weeks zero, two, and four. The study was carried out in Brazil and all subjects were of European descent. The research was grant-funded, although three of the authors received royalties from their patents on the tDCS devices used.

tDCS was delivered over both dorsolateral prefrontal cortices as a 2 mA current through a cap for 30 minutes. The sham cap mimicked the feeling of tDCS.

Using an intention-to-treat analysis, the researchers found that tDCS reduced self-reported ADHD symptoms by week four, with a large effect size of 1.23 (95% confidence interval 0.67–1.78). More patients guessed they were in the treatment arm than would be predicted by chance. A total of seven active and two control-group participants dropped out for various reasons, including dizziness and depression in the tDCS group. Only mild side effects were reported, and they were consistent with other tDCS research. Skin tingling or redness, scalp burning or pain, headache, and mood changes were the most common. The tDCS group completed an average of 20 sessions versus 24 in the sham group.

Carlat Take

Despite the positive findings for tDCS in ADHD, we’ll wait for replication. The small size, financial bias, and risks of unblinding give us pause.