Is it okay to have a nightlight on while sleeping?

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A parent asked us recently if light could be leading to her child’s night wakings. Ever since she’d turned 3, her daughter had been asking to have a light on — it had started out small, with the dim light from her sound machine, then the brightness was turned up a bit, and by the time she contacted us, her daughter was asking for a small string of lights to be kept on, the bedroom door to be open, and a hallway light to be on as she fell asleep. Basically it was starting to feel less like a dark cozy sleeping cave and more like a disco.

Artificial light during the night is confusing to the brain. In fact, a recent study from Northwestern showed that, even when we think we’re sleeping well, light in the sleeping environment disrupts our sleep patterns and our physiology. The brain’s master clock and circadian rhythms are activated and this can lead to lighter sleep and even metabolic changes that have negative health consequences. The body clock controls hormone levels and other physiological systems, and it is very attuned to light as a timing cue, so it’s easy to see how light signals during a period when we’re supposed to be sleeping would be unhealthy. The recent Northwestern study noted that exposure to even moderate ambient lighting during nighttime sleep, compared to sleeping in a dark room, harmed subjects’ cardiovascular function and increased insulin resistance the following morning.

This means that the gold standard is complete darkness during nighttime sleep, and this applies to all ages. Babies definitely don’t need nightlights — just have a dim light that can be turned on for feeding etc. if needed. Even preschoolers will do best sleeping without a nightlight (they can do it!). Teens often tell us they have LED lights in their bedrooms, which are fine in the evening but really need to be shut off before sleeping. Adults also sleep best in the complete darkness, so put up blackout curtains to block the neighbors’ lights or streetlights, do not have illuminated clocks in your room, and so forth.

As you know, gradually dimming lights during wind down and bedtime routines is an important prelude - imagine that you’re simulating the setting sun. Before you say goodnight, have one last step with your baby or child in complete darkness so their eyes can adjust, say goodnight and leave the room. Be sure not to leave lights on while kids are falling asleep and then turn them off later in the night, because this can become an unhelpful sleep association. (For more on fears of the dark, sleep associations, and independent sleep for little kids, check out the Little Kids Sleep Class.)

Even when we don’t think light is impacting our sleep, it is. Artificial light is, well artificial — it’s not meant to be on after the sun goes down. The more we can mimic what’s going on in nature, the better the whole family will sleep.