A landmark decade-long study has confirmed what many parents already feared: just one year of heavy social media use can seriously damage a young teenager's mental health.

Published in the Medical Journal of Australia and led by the Murdoch Children's Research Institute, the study tracked nearly 1,200 Melbourne children from ages 12 to 18. The results are stark.

For girls aged 12 to 13 who spent two or more hours a day on social media, researchers found about 11 additional cases of high depressive symptoms per 100 girls compared to those who used it for less than an hour. Boys in the same age group saw about seven extra cases per 100.

Dr Nandi Vijayakumar, a cognitive neuroscientist at Deakin University and the lead researcher, said the risk peaks in early adolescence for a few reasons. Puberty hits, and girls especially become more sensitive to peer approval and exclusion. At the same time, the parts of the brain responsible for emotion regulation are still developing.

"This is when young people first start using social media, typically, and learning how to navigate online interactions, but it's also a period of rapid brain development and important social changes," Vijayakumar said.

She added that adolescents might be less equipped to handle the harder parts of social media, like social comparisons and bullying.

"While the effects were modest at the individual level because this is so common among adolescents, even modest increases in risk could translate into potentially meaningful impacts at the population level."

Melbourne teenager Lauren Linton was 12 when COVID lockdowns hit, and her online use exploded. She relied on Snapchat to stay in touch with friends, but it came with a cost.

"I remember there being quite a bit of bullying and drama, and some of the girls would make group chats and leave the other girls out," Linton said. "You're so young at the time. You really don't understand the huge impact leaving somebody out like that can have on someone at an age when all you really want to do is fit in."

Her friend Kyra Prosser, who turned 18 in March, said her mother set a screen time limit that shuts down her apps after three hours. But she reckons most teens under 16 have found ways around the ban.

The study also found that boys aged 12 to 13 who spent hours online showed a slightly higher increase in self-harming behaviours than girls, even though girls generally had higher overall depression and anxiety.

These findings land six months after Australia introduced its controversial under-16 social media ban. Critics say it's hard to enforce, and data shows about 70% of kids who held accounts before the ban are still using them. Even the eSafety Commissioner, Julie Inman Grant, told this masthead she was "not really keen" on the ban, calling it legislation drafted "very quickly."

  • Study tracked nearly 1,200 Melbourne children from ages 12 to 18 over a decade
  • Published in the Medical Journal of Australia, led by Murdoch Children's Research Institute
  • For girls 12-13 using social media 2+ hours/day: 11 extra cases of high depressive symptoms per 100
  • For boys same age: 7 extra cases per 100
  • Risk peaked at ages 12-13 for both sexes
  • 70% of children who held accounts before the under-16 ban are still using them

The researchers say the study pinpoints a critical age window for intervention: early adolescence. That's when parents, schools, and policymakers might have the best shot at making a difference.

Prosser and Linton both said they still spend hours a day on Snapchat, TikTok, and Instagram. They see the good and the bad. "During the pandemic it became the only way we could stay in touch," Prosser said. "Now, we still use it all the time to chat or make plans to see other."