The objective of this study was to test the hypothesis that the regular practice 
of mindfulness meditation is associated with increased physiological levels of 
melatonin. Melatonin may be related to a variety of biologic functions important 
in maintaining health and preventing disease, including breast and prostate 
cancer. Previous studies have shown melatonin production is photosensitive and 
we suggest here that it also may be psychosensitive. A cross-sectional study of 
12-hour (20:00-08:00) urinary 6-sulphatoxymelatonin was conducted from which we 
analyzed data from 8 women who regularly meditate (RM) and 8 women who do not 
meditate (NM). All samples were collected in the homes of study participants. 
Volunteers were recruited to provide 12-hour overnight samples of urine. All 
subjects collected the samples on one night during the same 1-week period. There 
was no explicit intervention. However, all RM were either graduates of, or 
teachers in, the University of Massachusetts Stress Reduction and Relaxation 
Program. The main outcome measure was the total excretion of urinary 
6-sulphatoxymelatonin. Multiple linear regression (Proc GLM in SAS) was 
performed to test the effect of meditation (RM vs NM) on 6-sulphatoxymelatonin. 
The results of the study were that after controlling for the non-significant 
effect of menstrual period interval, we found an effect of meditation group (RM 
vs NM: b = 1.983; F = 6.78; p = 0.02) and age (for each integer year: b = 0.169; 
F = 8.41; p = 0.01). The conclusion is that study results are consistent with 
our hypothesis and indicate that melatonin might be a useful parameter in 
testing similar psycho-social interventions.(ABSTRACT TRUNCATED AT 250 WORDS)