BDNF and focal epilepsy: Based on the results presented in Fig. 2 and Table 2, our analysis using the IVW model suggested that each increased standard deviation (SD) in plasma BDNF decreased the risk of nITH (odds ratio [OR] = 0.861, 95 % confidence interval [CI]: 0.774–0.958, P = 0.006, PFDR = 0.078), epilepsy (OR = 0.927, 95 % CI: 0.880–0.976, P = 0.004, PFDR = 0.078), focal epilepsy (OR = 0.928, 95 % CI: 0.874–0.986, P = 0.016, PFDR = 0.139), and non-lesional focal epilepsy (OR = 0.981, 95 % CI: 0.964–0.999, P = 0.041, PFDR = 0.267).