Circadian rhythm, melatonin and screens
At Rowe & Associates, part of the Malu Health Group, we see firsthand how important sleep is for children’s development and wellbeing. When the brain is working well, it does some truly remarkable things. Beyond learning and managing emotions, one of its most important jobs is quietly regulating the sleep–wake cycle.
The Body’s Natural Clock
Many parents are familiar with the recommended hours of sleep for their child’s age (see below). What’s less widely known is that the brain is hardwired to protect those hours. That is because quality sleep is essential for growth, resilience, and overall health.
This process is guided by the circadian rhythm - a 24-hour cycle influenced by:
Light from the environment.
Lifestyle choices such as activity and exercise.
Hormones such as melatonin and cortisol.
The circadian rhythm helps the body:
Feel alert when the sun rises and drowsy as night falls.
Regulate body temperature across the day.
Control digestion depending on whether we are awake or asleep.
In short, this rhythm ensures our energy is used efficiently. Before artificial light, it helped humans thrive by staying active in the day and resting safely at night.
Hormones That Shape Sleep
As bedtime approaches, the brain releases melatonin. This hormone does not act like a sleeping pill, but it signals to the body that it is time to slow down, creating calm and preparing us for rest.
In the morning, the brain produces cortisol, which activates “go mode” and prepares the body for activity. These two hormones work in balance, rising and falling across the day.
Why Children May Struggle with Sleep
Every child needs sleep, but melatonin levels are not the same for everyone. Some children naturally produce melatonin later, which can delay the ability to fall asleep on schedule. *
Another critical factor is blue light. Sunlight is the strongest source, but TVs, computers, tablets, and phones also emit it. Blue light stimulates the brain to stay alert. Morning exposure is helpful, but evening exposure can confuse the circadian rhythm and make it harder for children to settle at night.
If your child struggles to fall asleep, and screens are part of the bedtime routine, this may be something to review. Limiting devices before bed can be a practical first step. In some cases, it may also be appropriate to discuss melatonin with your GP.
Recommended Sleep Hours by Age
Newborn (0–3 months): 14–17 hours
Infant (4–11 months): 12–16 hours
Toddler (1–2 years): 11–14 hours
Pre-school (3–5 years): 10–13 hours
School age (6–12 years): 9–12 hours
Teen (13–18 years): 8–10 hours
Adult (18+ years): 7 or more hours
* There is also increasing evidence that individuals with ASD or ADHD are among those who experience deficiencies in melatonin activity, i.e., delayed onset or reduced overall production.