The photo-biochemical basis of infant colic: pineal intracellular calcium concentrations controlled by light, melatonin, and serotonin.

Infant crying during the first 3 months of life exhibits a circadian rhythm with peak crying in the evening hours. Intracellular calcium ion within the pineal gland may be influenced by alternating light and dark, melatonin concentrations, and serotonin concentrations which both exhibit circadian rhythmicity. Differences in light by latitude and differences in the ontogenic development of melatonin and serotonin rhythmicity could combine to effect the pineal intracellular concentrations of calcium and result in high levels of infant crying called colic.