The newborn infant develops the components of circadian rhythm postnatally. A rhythm of cortisol develops at 8 weeks of age, melatonin and sleep efficiency develop at approximately 9 weeks, and body temperature rhythm and that of circadian genes develop at 11 weeks.

What age does circadian rhythm start?

Babies develop a circadian rhythm around four to six months of age, at which point they tend to sleep in larger blocks of time⁸. In adolescence, up to 16% of teenagers experience a sleep phase delay⁹. Due to this circadian shift¹⁰, their melatonin levels don't begin to rise until later in the evening.

Do babies have circadian rhythm?

Like us, babies have circadian rhythms, or biological processes that cycle about once every 24-hours. You can think of these rhythms as an internal clock, but there's a catch: The clock doesn't arrive pre-programmed.