A preliminary study published in European Psychiatry examined noninvasive brain stimulation as a possible avenue for treatment of auditory hallucinations. Auditory hallucinations that are not mitigated by antipsychotics affect approximately 30% of individuals with schizophrenia.
The trial included 22 patients who had been diagnosed with schizophrenia or schizoaffective disorder and experienced at least 3 auditory hallucinations per week. The participants had no hospitalizations 3 months prior to index and no dose change in antipsychotic medication 1 month before. Patients were excluded if they had a diagnosis of alcohol or substance dependence, seizures, a history of head or brain injury, exposure to anticonvulsant medication or daily benzodiazepines, or were pregnant.
Participants were randomly assigned to transcranial direct current stimulation, transcranial alternating current stimulation, and sham stimulation groups. Stimulation was administered twice a day for 20 minutes at a time for 5 consecutive days, with 3 hours between each administration. Symptoms were assessed on the Auditory Hallucination Rating Scale, the Positive and Negative Syndrome Scale, and Brief Assessment of Cognitive Schizophrenia.
While the stimulation was determined to be safe overall, with no participants dropping out because of low tolerability, some participants reported mild burning, itching, or tingling.
The study’s small participant pool did not allow for any significant findings. However, the authors pointed to a possible difference in the specific symptoms alleviated by different types of stimulation. Transcranial alternating current stimulation, in particular, had the largest effect size on auditory hallucinations from index to day 5, although sham stimulation had the largest effect size at 1 month. Transcranial direct current stimulation had a more notable effect on the items rated by the Positive and Negative Syndrome Scale and Brief Assessment of Cognitive Schizophrenia.
Previous research on noninvasive brain stimulation has produced mixed results. Transcranial current stimulation is less expensive and more portable than transcranial magnetic stimulation, making it a more accessible treatment for patients, but a consensus on its efficacy has not yet been reached.
Although this study was inconclusive, it may point in a direction for future research: targeting different symptoms with different brain stimulation techniques. The authors described a longer study with a larger sample size as necessary for understanding the treatment possibilities.
Mellin JM, Alagapan S, Lustenberger C, et al. Randomized trial of transcranial alternating current stimulation for treatment of auditory hallucinations in schizophrenia. Eur Psychiatry. 2018;51:25-33.