The main problem is the blue light that your smartphone screen emits. This attribute – shared with natural daylight – is designed to ensure that you can see what’s on your screen in bright sunlight.
Unfortunately, this similarity has an unwanted side effect. Because the light given off by your screen is the same as the light from the sun, your brain stops releasing the crucial hormone melatonin – and it’s this hormone that tells you that it’s time to go to sleep.
This isn’t a new phenomenon either. Research published in the journal Science in 1986 showed that exposure to bright lights can have a huge effect on the circadian pacemaker – a.k.a. your body clock – which sets your sleep patterns. But how else does bright light affect us?