A recent Swedish study has found that teenagers with longer screen times tend to have worse sleep.  The study, carried out by researchers at Karolinska Institute in Sweden, tracked over 4,800 Swedish students between the ages of 12 and 16 years old.  The team of researchers collected data on the students' sleep, depression symptoms, and screen time three times a year over the year.  The researchers found that these sleep disturbances have been linked to depression later in life for teenage girls but not teenage boys. Researchers found that 38%-57% of girls' depression symptoms were linked to changes in sleep patterns as a result of too much screen use.  The boy's data also showed sleep disruption; however, it did not link to later depression symptoms.  Measuring a healthy amount of screen time is difficult, as there is no specific amount of time set out by the American Academy of Pediatrics due to a lack of strong evidence. However, the Swedish Public Health Agency recommends that to promote better sleep, teenagers should limit their screen time to two to three hours a day maximum. The researchers believe that “if screen times were somehow reduced through public policy,” the rates of depression shown in their findings are likely to decrease.  Researchers noted that Swedish teens appear to exceed recommended screen time guidelines by only about an hour.