There are many potential causes of poor sleep in children, but regardless of the cause, it is important to be aware of overarching environmental factors that can affect sleep. The German word zeitgeber (literally “time-giver”) refers to any cue in the environment such as a change in light or temperature that can set the body’s internal clock. To sleep doctors, zeitgebers answer the question, “How does the brain know what time it is?” The brain predicts dawn and dusk based on 4 key variables: social interactions, exercise, light, and food (easy to remember using the mnemonic S-E-L-F). The best way to reset a child or adolescent’s circadian pattern is to modulate these 4 variables.

Social interaction. There is a difference between waking up and getting out of bed. Kids, like adults, need some incentive to get up in the morning and get going. Hobbies and social relationships play a key role here. One challenge is that, for a lot of kids, social interactions outside of school take the form of online activities like gaming and various forms of social media. If they are online at night and therefore fighting sleep, then the next day they will be sleeping in the back of the car, the bus, or during class time. Encourage parents to help kids do something exciting and engaging first thing in the morning rather than late at night.

Exercise. The main question to ask children or adolescents with sleep problems is, when do they get outside to play or exercise? How often, how long, and during what time of day? For resetting the circadian cycle, if you have a kid who is fighting sleep in the afternoon, then that would be a good time to go for a walk, exercise, or engage in outdoor playtime, depending on the age, rather than napping.

Light. Kids need bright light in the morning and darkness at night. For years, parents have mistakenly been responding to kids who fear the dark or fear being alone at night by supplying them with light—such as a nightlight or leaving the bathroom light on with the door open. Sleep experts try to point out to parents that the children are not really scared of the dark; rather, they have associated the dark with being alone. The whole idea of putting them alone in a quiet room is something we have to teach kids to do, and naturally some will be apprehensive or scared or even get nightmares. It is important to teach kids to equate darkness with sleeping so that you’re not inadvertently disrupting their natural circadian rhythm.

Food. Food and light are strongly connected. I sometimes explain this by using the example of experiments with rats. Rats are normally nocturnal creatures—they sleep during the day and are active at night. But if you put a rat in a cage and only give it food when the lights are on, eventually it will associate light with food—and you can transform a rat from being nocturnal to diurnal this way. Many kids, especially teenagers with irregular sleep/wake schedules, tend to eat at all different times of the day instead of at established, regular meal times that coincide with the natural light cycles. Eating at predictable times every day helps to normalize a kid’s circadian rhythm.