Treating auditory hallucinations with transcranial direct current stimulation in a double-blind, randomized trial

Objective: Transcranial direct current stimulation (tDCS) could be a treatment option for medication-resistant auditory hallucinations (AH), but so far results have been inconclusive, and large sample trials have been missing. This study used tDCS as a treatment method for these hallucinations in a double-blind, placebo-controlled study with a relatively large sample size. Methods: Fifty-four patients of several diagnostic categories with medication-resistant AH were randomized and treated during 10 sessions of 20 min each, with either 2 mA tDCS or placebo, administered on five consecutive days (i.e., two sessions per day). Anodal stimulation was targeted at the left dorsolateral prefrontal cortex, cathodal stimulation at the left temporoparietal junction. AH severity was assessed using the Auditory Hallucination Rating Scale (AHRS). Other outcome measures were assessed with the Positive and Negative Syndrome Scale (PANSS), the Stroop, and the Trail Making Test. Results: AH frequency and severity decreased significantly over time, as did the scores on the total and general subscales of the PANSS. However, there was no significant interaction effect with the treatment group on any of the main outcome measures. Conclusions: We found no evidence that tDCS is more effective for medication-resistant AH than placebo, even though AH frequency and severity decreased in both groups. An alternative strategy may be to offer tDCS at an earlier stage of illness. In the light of recent investigations into the neurophysiological mechanisms behind tDCS, we may also have to consider the possibility that tDCS is not able to induce any long-lasting brain changes