RESUMO
BACKGROUND: Obsessive-compulsive disorder (OCD) is a common psychiatric disorder. The Food and Drug Administration (FDA) approved repetitive transcranial magnetic stimulation (rTMS) to treat OCD in 2018. So far, various approaches to treat this disorder have been evaluated. We evaluated the effect of adjunctive low-frequency rtMS over the left dorsolateral prefrontal cortex in patients with OCD refractory to treatment. METHODS: The present clinical trial was done on 37 patients with OCD referring from the psychiatry clinic, 22 Bahman Hospital, Qazvin province, between 2018 and 2020 and patients were randomly divided into two groups. The intervention group received rTMS treatment at 1 Hz for 20 min (1200 pulses/day) over the left DLPFC area as adjunctive to the medical treatment three times a week and for five weeks, whereas those in the control group were subjected to only the sham condition plus their medical treatment. The Yale-Brown Obsessive-Compulsive Scale (Y-BOC.S) was completed by patients before the study, following sessions 5 and 10 during the intervention, at the end of the intervention, and three to six months after the intervention under the direct supervision of a psychiatrist. SPSS software version 26 was used to compare the results between the two groups. RESULTS: The intervention group showed significantly lower mean Y-BOCS scores after the intervention and at follow-up (P < 0.05) and all patients of the intervention group showed significantly lower Y-BOCS scores than their own baseline scores (P < 0.05). Also, using antipsychotic agents along with the serotonergic agents yielded significantly lower scores in the intervention group at the end of the intervention (P < 0.05). All the patients were found with higher follow-up scores than their scores at the end of the intervention; however, this difference was not significant (p > 0.05). CONCLUSION: Adjunctive low-frequency (1 Hz) rTMS over the left DLPFC is able to effectively reduce Y-BOCS score in OCD patients refractory to treatment following 15 sessions, and the reduction was durable even after three to six months. Using antipsychotic agents as an adjuvant with serotonergic agents was identified as a possible predictor for response to adjunctive rTMS therapy.