Repetitive transcranial magnetic stimulation (rTMS) fails to increase serum brain-derived neurotrophic factor (BDNF).

Objectives: Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal plasticity and in the pathophysiology of various brain disorders. Repetitive transcranial magnetic stimulation (rTMS) has been widely used in neuropsychiatric disease. It is presumed that BDNF mediates the therapeutic benefits of rTMS, but previous results are contradictory. We therefore conducted a meta-analysis to examine the efficacy of rTMS to increase serum BDNF.

Methods: We performed a comprehensive literature search for clinical trials evaluating the efficacy of rTMS and addressing serum BDNF level. To pool effect size estimate (Hedges' g) of serum BDNF across studies, a meta-analysis was performed according to the Cochrane guideline.

Results: rTMS failed to increase serum BDNF level with effect size of -0.12 (95% CI: -0.30, 0.06) (P=0.193). Multilevel mixed-effects models analysis showed that overall effect of rTMS on BDNF levels was influenced by group of participants (healthy vs. disease) (P<0.001), stimulation frequency (low-frequency vs. high-frequency) of rTMS (P=0.007), treatment duration (P<0.001) of rTMS, and population age (P<0.001).

Conclusions: Repetitive rTMS fails to increase serum BDNF, and it seems that serum BDNF level is related to frequency and duration of rTMS, as well as age and health status of population.