BDNF and Parkinson disease: As shown in Table 1 and Figure 1A, the serum BDNF levels in PD patients with RLS was significantly lower than that in PD patients without RLS, controls without RLS, and controls with RLS (PD with RLS, 2604.40 ± 1011.22 pg/ml; PD without RLS, 3814.57 ± 835.38 pg/ml; controls without RLS, 4779.18 ± 771.59 pg/ml; controls with RLS, 3502.63 ± 904.08; p < 0.001; effect sizes = 1.30, 2.42, and 0.94, respectively).