To assess the efficacy and safety of transcranial direct current stimulation (tDCS) in improving pseudoword reading performance and associated outcomes in individuals with developmental dyslexia in comparison to sham.

Ten RCTs (249 patients;125 underwent active tDCS) were identified. Active tDCS produced a significant improvement in rapid automatized naming–letters (MD = −1.08;95% CI−2.04 to−0.11;p=0.03; I²=20%). Long-term pseudoword retention favor active tDCS (SMD=0.62;95 %CI 0.05 to 1.19;p=0.03;I²= 50%), along with low-frequency word accuracy (MD =0.49;95% CI, 0.03 to 0.95;p =0.04;I² =46%).No significant differences were found for pseudoword reading accuracy (SMD =0.32;95% CI −0.08 to 0.72;p=0.11;I² =0%), speed (SMD =0.10;95% CI−0.27 to 0.47; =0.60;I² =0%), fluency - text (SMD =−0.01;95% CI−0.54 to 0.51;p =0.96;I²=0%), low-frequency (MD =0.59;95% CI−6.12 to 7.31;p =0.86;I²=0%) and high-frequency (MD =−0.34;95% CI−4.20 to 3.53;p =0.86;I²=0%) or phonological awareness, including phoneme blending accuracy (MD=0.02;95% CI−1.26 to 1.21;p=0.97;I²=0%) and phoneme blending time (MD=−2.04;95% CI−9.85 to 5.77;p=0.67;I² = 0%). Total adverse event risk was higher with sham (RR=2.08;95% CI 1.28–3.38;p=0.003;I²=0%).

tDCS did not significantly improve reading outcomes in comparison to sham in developmental dyslexia. However, small benefits were seen in rapid naming tasks. The current evidence does not support routine clinical use. Larger trials are needed to determine its role as an adjunct therapy.