Melatonin, also known as the ‘sleep hormone’, is available in supplement form but it is naturally produced by the body. “The hormone is released into the bloodstream by the pineal gland, which is an endocrine gland located in the middle of the brain,” Dr Meadows explains.

Melatonin production is brought on by increased darkness and triggers feelings of tiredness, helping us regulate our sleep cycles. “The light-sensitive cells in our eyes are able to detect the changes in light, which, via our body clock, instruct the pineal gland to release melatonin,” says Dr Meadows.

This is one of the reasons why our body clocks are in line with the world’s natural rhythms of light and darkness. It’s also why experts advise against using digital devices before bed, as the light emitted from them can inhibit melatonin production, which could prevent you from being able to fall asleep.

It’s not just about when we stop seeing light, but also when we start. Our circadian rhythm kicks in again when we wake up, and it’s thought that morning sunlight sets a 12-hour timer in the body to start producing melatonin.

Melatonin: how the hormone impacts sleep and the circadian rhythm