Facebook Inc. is losing its swagger with young users, who are increasingly migrating to rival platforms including Snap Inc.’s Snapchat, according to a new study.

Facebook will lose 2 million users under 25 in the U.S. this year while Snapchat will add 1.9 million, EMarketer Inc. said Monday, citing its own report. Facebook usage among kids younger than 12 will drop more than 9 per cent, with declines of about 6 per cent each among 12- to 17-year-olds and 18- to 24-year-olds.

In the U.K., 71 per cent of social network users between 12 years and 17 years old will be using Facebook regularly this year, a downgrade of 8 points from last year’s forecast, EMarketer said. Snapchat will get log-ins from 43 per cent of U.K. social networkers in 2018, more than double the number three years ago.

Facebook has tried to stem an exodus to Snapchat with measures such as a new version of its Messenger app for children. While the overall number of Facebook users will reach 169.5 million in the U.S. and 32.6 million in the U.K. this year -- far more than Snapchat, Instagram or Twitter can claim -- the drop among younger users means Facebook’s "teen issue" is more than just a theory, said Bill Fisher, an analyst at EMarketer.

“There are now some early signs that younger social networkers are being swayed by Snapchat,” Fisher said. “The challenge and opportunity for Snap is how to appeal beyond that core youth demographic.”

Technology companies are also facing increasing pressure to address their impact on the mental health of children. In an open letter to Apple Inc. dated Jan. 6, activist investor Jana Partners LLC and the California State Teachers’ Retirement System urged Apple to create ways for parents to restrict children’s access to their mobile phones. They also want the company to study the effects of heavy usage on mental health.

Nicola Mendelsohn, Facebook’s vice president for the EMEA region, said she actively limits the time her own children are allowed to use their phones.

"I take phones off my kids at night and we charge them in the hall at home," she said in an interview Friday. "I actually think it’s good for kids to have a break from it."