The effects of long meditation on plasma melatonin and blood serotonin.

Abstract

The findings suggest that advanced meditators have higher melatonin levels than non-meditators. Melatonin decreases during long meditation, a finding the study does not explain. Serotonin declines after both one-hour meditation and rest, indicating that serotonin may be a marker of general rest and not meditation-specific relaxation.