Importance: Negative symptoms represent a substantial burden in schizophrenia. Although preliminary studies have suggested that transcranial direct current stimulation (tDCS) is effective for some clusters of symptoms, the clinical benefits for negative symptoms are unclear.
Objective: To determine the efficacy and safety of tDCS vs sham as an add-on treatment for patients with schizophrenia and predominant negative symptoms.
Design, setting, and participants: The double-blind Schizophrenia Treatment With Electric Transcranial Stimulation (STARTS) randomized clinical trial was conducted from September 2014 to March 2018 in 2 outpatient clinics in the state of São Paulo, Brazil. Patients with schizophrenia with stable negative and positive symptoms and a minimum score of 20 points in the negative symptoms subscale of the Positive and Negative Syndrome Scale (PANSS) were included.
Interventions: Ten sessions of tDCS performed twice a day for 5 days or a sham procedure. The anode and the cathode were positioned over the left prefrontal cortex and the left temporoparietal junction, respectively.
Main outcomes and measures: Change in the PANSS negative symptoms subscale score at week 6 was the primary outcome. Patients were followed-up for an additional 6 weeks.
Results: Of the 100 included patients, 20 (20.0%) were female, and the mean (SD) age was 35.3 (9.3) years. A total of 95 patients (95.0%) finished the trial. In the intention-to-treat analysis, patients receiving active tDCS showed a significantly greater improvement in PANSS score compared with those receiving the sham procedure (difference, 2.65; 95% CI, 1.51-3.79; number needed to treat, 3.18; 95% CI, 2.12-6.99; P < .001). Response rates for negative symptoms (20% improvement or greater) were also higher in the active group (20 of 50 [40%]) vs the sham group (2 of 50 [4%]) (P < .001). These effects persisted at follow-up. Transcranial direct current stimulation was well tolerated, and adverse effects did not differ between groups, except for burning sensation over the scalp in the active group (43.8%) vs the sham group (14.3%) (P = .003).
Conclusions and relevance: Transcranial direct current stimulation was effective and safe in ameliorating negative symptoms in patients with schizophrenia.
Trial registration: ClinicalTrials.gov identifier: NCT02535676.