Positives

• A randomized, sham-controlled trial in Long COVID patients found that home-based intranasal plus transcranial 40 Hz photobiomodulation produced measurable cognitive improvements, particularly in patients under 45 medRxiv.
  
  
• Patients reported high adherence and no serious adverse effects in the home photobiomodulation cohort PMC.
  
  

Negatives

• Some fatigue and mobility measures favored sham over active photobiomodulation, with researchers noting that as cognitive function improved patients sometimes became more aware of residual physical fatigue medRxiv.
  
  
• Patients over 45 in the trial saw smaller cognitive gains than younger patients, suggesting age-related response variability medRxiv.
  
  

Hurdles & Side Effects

• The 40 Hz transcranial-plus-intranasal photobiomodulation system is generally several thousand dollars and not insurance-covered for Long COVID brain fog medRxiv.
  
  
• Patients commit to a 20-minute session 3-5 times weekly over multiple weeks before drawing conclusions, which is difficult during cognitive crashes medRxiv.