Intensive Home-based Transcranial Direct Current Stimulation for Long COVID

This is a randomized, double-blind, sham-controlled, crossover clinical trial designed to evaluate the efficacy, safety, and adherence of a home-based transcranial direct current stimulation (tDCS) program for adults suffering from Long COVID. Background and Rationale: Long COVID is characterized by persistent, debilitating symptoms following acute SARS-CoV-2 infection, with fatigue, cognitive dysfunction ("brain fog"), pain, anxiety, and depression being among the most prevalent and disabling manifestations. Non-invasive brain stimulation, specifically tDCS targeting prefrontal regions implicated in cognitive and affective regulation, represents a promising neuromodulatory therapeutic approach. This trial investigates whether a home-based tDCS protocol can be safely and effectively administered in a real-world setting to improve clinical outcomes. Study Design and Intervention: A total of 40 eligible participants are randomized in a 1:1 ratio into one of two treatment sequences: * Sequence 1: Sham tDCS during Period 1, followed by a 4-week washout period, and active tDCS during Period 2. * Sequence 2: Active tDCS during Period 1, followed by a 4-week washout period, and sham tDCS during Period 2. Each treatment period utilizes a 3-week tapered schedule comprising a total of 42 sessions per intervention: * Week 1: 3 sessions per day (morning, afternoon, evening; 21 sessions total). * Week 2: 2 sessions per day (morning, afternoon; 14 sessions total). * Week 3: 1 session per day (any time of day; 7 sessions total). Assessments and Safety: Participants undergo rigorous clinical evaluations at baseline, at the end of Phase 1 (following 42 sessions), and at the end of Phase 2 (following crossover and completion of the second 42 sessions). The primary outcome is fatigue severity assessed via the Fatigue Assessment Scale (FAS). Secondary outcomes include cognitive performance (MoCA), pain intensity (VAS), anxiety and depression symptoms (HADS-A and HADS-D), and health-related quality of life (PROMIS-G10). Home adherence rates and side effect profiles are prospectively monitored throughout the protocol to evaluate the real-world scalability and safety of unsupervised, home-based tDCS administration.