Randomized controlled trial of four protocols of repetitive transcranial magnetic stimulation for treating the negative symptoms of schizophrenia

BACKGROUND: The negative symptoms of schizophrenia are not effectively treated with antipsychotic medications. Repetitive transcranial magnetic stimulation (rTMS) is an alternative approach that may be more effective in treating negative symptoms, but there has been little research comparing the effectiveness of different rTMS stimulation protocols. OBJECTIVE: Compare the effect of four different rTMS protocols in the treatment of the negative symptoms of schizophrenia. METHODS: Ninety-six patients with schizophrenia who had prominent negative symptoms were randomly assigned to four treatment groups: 10 Hz, 20 Hz, theta burst stimulation (TBS), and mock rTMS (i.e., the control group). In the first three groups, the left dorsolateral prefrontal cortex was stimulated at 80% of the motor threshold five times per week for four weeks. Before and after the treatment, evaluators who were blind to the group assignment of patients administered the Positive and Negative Syndrome Scale (PANSS), the Scale for the Assessment of Negative Symptoms (SANS) and the Treatment Emergent Symptom Scale (TESS). RESULTS: Three of the 96 patients dropped out during the trial (two from the control group and one from the 20 Hz group). Compared to the control group, after 4 weeks of rTMS treatment all three treatment groups had lower scores on the PANSS negative symptom subscale, the PANSS general psychopathology subscale, and the SANS. The TBS group had significantly larger reductions in these scores than the 10 Hz group and the 20 Hz group, but there were no significant differences between the 10 Hz and 20 Hz groups. There were no pre- versus post-treatment differences in the PANSS positive symptom subscale scores between the four groups. No serious adverse events occurred and there were no statistically significant differences in the TESS scores across the four groups. CONCLUSIONS: We find that rTMS, particularly the TBS stimulation protocol for rTMS, is a safe and effective treatment method for patients with schizophrenia who have prominent negative symptoms. Longitudinal studies with large samples are needed to optimize the rTMS treatment, to identify the stimulation protocol, duration, intensity and treatment interval that provides the best therapeutic result at the lowest risk to the patient.