Safety and Blinding of Transcranial Direct Current Stimulation in Schizophrenia Patients

Transcranial direct current stimulation (tDCS) is a method of noninvasive brain stimulation. tDCS clinical efficacy is debatable, but it was proved to be effective at the neurophysiological level. tDCS has a very good safety profile in human subjects. Because the method has been more frequently studied in patients with schizophrenia, we wanted to analyze the safety and tolerability of tDCS treatment in this population. We also evaluated blinding quality of tDCS stimulations.

All stimulations were performed using the DC-Stimulator PLUS (neuroCare, Germany) with the sham module installed. For all the stimulations, 2.0-mA current and 5 × 7-cm anode and cathode rubber electrodes in saline-soaked sponges were used.

We collected and evaluated safety data in a large dataset of 1139 tDCS stimulations in patients with schizophrenia. No serious adverse events were recorded. None of the subjects discontinued tDCS treatment due to side effects. All the reported events resolved spontaneously within 30 minutes after the tDCS session. In approximately 17% of all the stimulations, no side effects were reported by the patients. The 2 most frequent types of side effects were itching/tingling (reported by 68.4% of the subjects) and burning/warmth sensations (57.4%, when combined).

This study confirms that tDCS is safe and well tolerated by patients with schizophrenia. The most frequent side effects are itching/tingling and burning/warmth sensations, all of low severity. We found that blinding of tDCS stimulations is imperfect. We recommend that blinding assessment become a routine part of sham-controlled tDCS studies.