You just got into bed after a long day, and you're exhausted. You plan to spend a few minutes on your phone — maybe scrolling Instagram or TikTok — and then sleep. But when you try to sleep, it's not as easy as you thought it would be. You were so tired — what happened? According to a new study, your phone may be the problem. The study, done by researchers at New Zealand's University of Otago, involved 85 kids aged 11 to 14. They each spent a week wearing a body camera on their chest starting from three hours before they got into bed. A second camera was also placed in their bedrooms to monitor their phone use once they were in bed. They also wore a device that tracked their sleep. The researchers found that 99% of the participants used their phones in the two hours before bed. More than half used their phones while they were in bed, and about a third used their phones after trying to go to sleep. The results showed that screen time in bed affected participants' sleep — it stopped them from going to sleep for about half an hour, and also reduced the amount of sleep they got. The impact was larger when participants had a more interactive experience — such as playing a game — or if they used more than one screen. For every additional 10 minutes of this type of screen time, sleep time was reduced by the same amount. Interestingly, phone use in the two hours before bed had little impact on sleep. According to lead researcher Bradley Brosnan, the results suggest that, while current guidelines recommend no screen time in the hour or two before bed, keeping phones out of the bedroom might be enough for a better night's sleep.