Middle schoolers who spend time on smartphones, laptops, and tablets in the hour before bed are likely to sleep poorly and be more tired the next day, a new study shows. Researchers looked at the effects of screen time at bedtime among 345 children aged 12 to 14 over a six-month period. They found that spending time on media devices before going to bed disrupted sleep and had a “bidirectional” effect such that poor sleep led to more bedtime media use. “So it creates this vicious cycle where engaging in bedtime media use can result in poor quality sleep, which over time fuels more bedtime media use,” said Atika Khurana, an associate professor in the Counseling Psychology and Human Services Department at the University of Oregon and research scientist at the Prevention Science Institute. “Just having access to screen-based media devices in bedrooms has been associated with poor sleep quality …