The Role of iTBS in Bipolar II Depression

There is a paucity of evidence-supported treatment choices for bipolar II depression (BD-II depression), hindered by multiple comorbidity and manic switch. In addition, a slower response also burdens the patients. Intermittent theta-burst stimulation (iTBS) is a new form of Repetitive transcranial magnetic stimulation (rTMS) which is more powerful and requires less time of operation (i.e., about 1/3 of traditional treatment time) compared to traditional rTMS protocols. The antidepressant effect of iTBS for major depressive disorder is well established; however, its effect for BD-II depression is still undetermined with few investigations. In the current study, the investigators plan to conduct a randomized, controlled study to directly compare antidepressant effects of iTBS (n=30) versus sham (n=30) for BD-II depression under treatment of quetiapine monotherapy. The participants will receive 10 times of iTBS sessions in 2 weeks (daily from Monday to Friday and off on the weekends for 2 weeks), followed on the end of week 2 (right after treatment,), week 6 and week 12. The investigators hypothesize that iTBS is effective for BD-II depression and may improve cognitive decline associated with BD-II. In addition, the investigators have identified several microRNAs (miRNAs) (miR-7-5p, miR-142-3p, miR-221-5p, and miR-370-3p) which may aid the diagnosis of BD-II and such diagnostic model was patented in Taiwan. The investigators further found significant correlations with these miRNAs with peripheral levels of brain derived neurotrophic factor (BDNF). The investigators inferred that these miRNAs may be associated with susceptibility with BD-II thru modulation of BDNF. Because modulation of BDNF level is one of the anti-depression mechanism for rTMS, the investigators plan to monitor the changes of these candidate miRNAs and BDNF levels in serum before and after iTBS treatment (week 0, 2,6,12), in attempt to clarify whether these miRNAs may be treatment biomarker as well. T