Young children start differentiating day from night around 3 months of age. This is due to a newborns circadian rhythm (internal biological clock) developing by 12 weeks of age. Research shows that there are multiple factors that promote day and night.
A circadian rhythm is set by food, light and socialisation. That being, it is a realistic expectation that newborns feed both day and night, however feeding in a dimmed or dark room during the night can assist the establishment of a circadian rhythm (darkness promotes the secretion of melatonin – sleep hormone). Alternatively during the day and when a child isn’t napping, promote natural light as this encourages awake time. Lastly, socialisation and games while awake, sets up day expectations and routine.
Internal body clocks are controlled by the production of hormones, such as melatonin and cortisol and influence our day and night routine. Around 3 months cortisol levels are highest in the early morning, promoting ‘being awake’. Meanwhile, melatonin is highest from 6pm and continues overnight, hence promoting ‘sleep time’.
Body temperature rhythms appear and naturally fluctuate by 6 weeks of age. Body temperature rises during the day and lowers in the evening, making our bodies ready for sleep.
Lastly, some evidence supports breastfeeding as a way to help a newborn differentiate day from night. Australian Breastfeeding Association states that “Breast milk has an amino acid (tryptophan) that is used by the body to make melatonin. Tryptophan levels increase and decrease with a mother’s circadian rhythm, so breastfeeding may help develop a baby’s circadian rhythm”. I reassure mothers that if not breastfeeding there are other elements that influence the circadian rhythm and be reassured if you are unable to breastfeed.