Transcranial Direct Current Stimulation for Developmental Dyslexia: A Systematic Review and Meta-analysis of Randomized Controlled Trials
Abbas Hussain1, Aziz Ur Rehman2, Mohammad Daniyal3, Talha Ali4, Rahma naveed5, Muhammad Huzaifa Khattak6, SARAH AZHAR7, Huzaifa Nawaz8, Syeda Ramish Zehra Kazmi9, Safa Shahid10, Dhyey Sidhpura11, Aisha Rizwan Ahmed12
1Jinnah Medical and Dental College, karachi, Pakistan, 2Jinnah Medical And Dental College, Karachi, Pakistan, 3Isra university Hyderabad, 4Shaheed Mohtarma Benazir Bhutto Medical College Lyari, Karachi, Pakistan, 5Jinnah medical and dental college, karachi, Pakistan, 6Khyber Medical College, 7Jinnah Medical and Dental college, 8Services Institute of Medical Sciences (SIMS), Ghaus-ul-Azam Jail Road, Lahore, Pakistan 54000, 9Liaquat National Hospital and Medical College, Karachi, Sindh, Pakistan., 10Liaquat National Hospital and Medical College, Karachi, Sindh, Pakistan, 11Carle foundation Hospital Urbana Illinois, 12Liaquat University of Medical and Health Sciences, Jamshoro, Pakistan
Objective:
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.
Background:
Developmental dyslexia impacts 5 to 10% of children globally and is marked by diminished activation in left-hemisphere reading circuits. tDCS has surfaced as a possible complement to behavioural therapies; nonetheless, variable stimulation regimens and small, heterogeneous trials have constrained definitive findings about its clinical efficacy.
Design/Methods:
We searched seven databases (PubMed, Embase, Scopus, ClinicalTrials.gov, PsycINFO) from inception to October 2025 for RCTs of tDCS on dyslexia. The primary outcome was pseudoword reading. Additional outcomes were word reading, fluency, phonological and cognitive measures, long-term retention, and side effects. The pooled SMD or MD with 95% CI were calculated by random-effects models.
Results:
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%).
Conclusions:
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.
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