Laughter increases the levels of melatonin in breastmilk. Mothers who viewed a humorous 87 minute DVD compared to an 87 minute DVD on the weather demonstrated increased levels of breastmilk melatonin. This occurred in both allergic and healthy mothers. Feeding infants with milk that contained increased levels of melatonin reduced allergic responses in infants with allergic eczema. Hmmm- as melatonin influences sleep/wake cycles, maybe sleep-deprived mothers should laugh it up prior to that last breastfeeding before going to bed!

Kimata, H. (2007). Laughter elevates the levels of breastmilk melatonin. Journal of Psychosomatic Research, 62, 699-702.