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Does my baby need to sleep in complete darkness?

The short answer is yes – and no!

The biggest factor in differentiating between day and night is exposure to light. This is what sets an infant’s circadian rhythm, which begins to develop around six weeks of age and is usually set between three and six months (Yates, 2018). Darkness at night supports consolidates sleep, and exposure to light can interfere with this.

Darkness plays a key role in setting a person’s circadian rhythm (our internal clock), but most of the research looks at darkness as beneficial for nighttime sleep. Too much exposure to light leading up to bedtime can inhibit the body’s production of melatonin (the hormone we need to help us get to sleep), and research has shown that too much light exposure during nighttime sleep can have impacts on our health (Yates, 2018).

While darkness is beneficial at night, naps are a bit of a different story. Full darkness is not critical for daytime sleep. Some babies are easily distracted and do better with a dark room, but pitch blackness can often too closely mimic nighttime sleep, resulting in very long naps that may impede consolidated nighttime sleep. Additionally, if your baby can sleep with some light exposure, there is no scientific reason to eliminate this during the daytime.

A study by Cornwell and Feigenbaum in 2006 demonstrated that infants at low risk of SIDS had more time awake during the day and more time asleep at night relative to infants at high risk of SIDS (Cornwell AC, Feigenbaum P. Sleep biological rhythms in normal infants and those at high risk for SIDS. Chronobiol Int. 2006;23(5):935–961), so getting that consolidated sleep at night is more important than having very long daytime naps.

If your baby is easily distracted by sources of light, or if they are sensitive to light exposure, there may be value in darkening their sleep space. This is particularly important in the summer months for nighttime sleep, when the sun sets late and rises early. In these instances, blackout blinds can be really helpful. I’ve tried a few of the most popular blackout solutions and personally recommend the SleepOut for a great portable blackout solution – use code CAYLA for 10% off your purchase (full disclosure: I do receive a small commission when you use this code, but am very selective of what I promote and use this product in my own home).

Struggling to find sleep solutions to meet your family’s needs? Let’s chat!


Yates J. The long-term effects of light exposure on establishment of newborn circadian rhythm. J Clin Sleep Med. 2018;14(10):1829–1830.

Cornwell AC, Feigenbaum P. Sleep biological rhythms in normal infants and those at high risk for SIDS. Chronobiol Int. 2006;23(5):935–961

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