Smartphones have a sad effect on mental health for young women.

More time spent in front of a cell phone or computer screen can lead to increased symptoms of depression and, in severe circumstances, suicide-related behaviors and thoughts in female teens, according to a new study by San Diego State University.

Researchers surveyed 500,000 U.S. teens over the course of more than a decade, asking them how they spent their free time, and looked at data suicide statistics kept by the U.S. Centers for Disease Control and Prevention. They found that the suicide rate for young women between 13 and 18 increased by 65% between 2010 and 2015, and the number of girls having suicidal thoughts — such as feeling hopeless and thinking about self harm — rose by 12%. The number of teen girls reporting symptoms of bad depression rose by 58%.

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“Between 2010 and 2015, teens increasingly spent more time with screens and less time on other activities. That was by far the largest change in their lives during this five-year period, and it’s not a good formula for mental health,” San Diego State University psychology professor Jean Twenge, who looked back at data to see if there was a correlation with screen-time and depression and suicidal tendencies, said.

Researchers found that 48% of teens who spent five or more hours per day on electronic devices reported at least one suicide-related outcome, compared to just 28% of those who spent less than an hour a day on devices. Symptoms of depression were also more common in teens who spent a lot of time on tablets, computers and smartphones as well.

It’s possible that girls are more prone than young men to experience these negative mental health effects due to social media apps like Instagram, Snapchat and Facebook where they can feel pressure to look a certain way and keep up with appearances of others on their newsfeeds, experts say.

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“What I see occurring is what I call vanity validation. While women are using social networks to interact, they still use real world indicators to value themselves in comparison to others. It’s more emotionally driven,” says behavioral scientist Clarissa Silva. “The main trigger is feelings of jealousy. They could be looking at aspects that are missing from their lives. Males may experience jealousy, but not in the same way women do.”

Meanwhile, those who spent time socializing and playing sports or exercising were said to have fewer depressive symptoms, the study notes. Twinge suggests limiting screen-time to just one or two hours per day to be safe.