Results indicate that grounding the human body to earth during sleep reduces night-time levels of cortisol and re-synchronizes hormone cortisol secretion more in alignment with the natural 24-hour circadian rhythm profile.
24 hours cortisol secretion

Earthing: Health Implications of Reconnecting the Human Body to the Earth's Surface Electrons
The biologic effects of grounding the human body during sleep as measured by cortisol levels and subjective reporting of sleep, pain, and stress.
Pilot Study on the Effect of Grounding on Delayed-Onset Muscle Soreness
Earthing the Human Body Influences Physiologic Processes
Changes in pulse rate, respiratory rate, blood oxygenation, perfusion index, skin conductance, and their variability induced during and after grounding human subjects for 40 minutes.
Can electrons act as antioxidants? A review and commentary.
Earthing (grounding) the human body reduces blood viscosity-a major factor in cardiovascular disease.
Chronic Disease: Are We Missing Something?
EARTHING ADVICE ON PAGE 25