Social media may be fuelling eating disorders in children as young as 12, research suggests.
Scientists from Flinders University in Adelaide looked at almost 1,000 students aged 12-to-14.
More than half (52%) of the female participants showed signs of anorexia, bulimia or binge eating, including overexercising or skipping meals.
These behaviours were more common among those with several social-media accounts, the results show.
The scientists worry posting and commenting on pictures online drives “thin-ideal internalisation”.
Around 1.25 million people in the UK are thought to have an eating disorder, of which three quarters are female, according to the UK charity Beat.
In the US, at least 30 million people are said to suffer, National Association of Anorexia Nervosa and Associated Disorders statistics show.
Social media is increasingly being linked to poor mental health, however, its effect on eating disorders was less clear.
To learn more, the Australian scientists asked students from five private schools about their social media use. Eating disorders were “diagnosed” according to a survey used by medics.
While more than half of the girls showed red flags, 45% of the male participants also demonstrated worrying eating habits, up to twice as many as feared.
Results - published in the International Journal of Eating Disorders - revealed three quarters (75%) of the girls and 70% of the boys used social media.
The more accounts they had, and the longer they spent on them, the higher their eating disorder risk, the results suggest.
“It was notable girls were more likely to post pictures of people than boys on Instagram and Snapchat,” lead author Dr Simon Wilksch said.
“This did not apply to selfies, but to pictures taken by others of the participant, as well as pictures of friends and celebrities.
“These respective findings suggest girls have a greater focus on appearance and food than boys and fits conceptually with girls having increased disordered eating risk.
"They were also consistent with previous findings that elevated appearance focused activity on social media (e.g. commenting on photos, posting photos) was associated with higher levels of thin-ideal internalisation, drive for thinness and weight dissatisfaction in high school females.”
Eating disorders were most common among girls with Snapchat and Tumblr, while Snapchat, Facebook and Instagram “raised the risk” in the boys.
“This needs to be addressed given that 13 years is the minimum required age for accessing many social-media accounts and early adolescence is a time of increased disordered eating risk,” Dr Wilksch said.
“Further, given that media literacy is the leading approach to risk reduction in young-adolescence, if social media is associated with increased disordered eating risk, content targeting social media use could readily be incorporated in such programmes.”
Half of the participants did not “follow” a parent on Snapchat, which could help mitigate the risk.
“Parents have an important role to play in their child's early use of social media where one study has found control over time spent is associated with greater life satisfaction in pre-adolescent girls and boys,” Dr Wilksch said.
“While it is acknowledged this strategy becomes less feasible and effective beyond the late childhood years, it might go some way to reducing possible harm when the child is still young and vulnerable, similar to how television viewing has been traditionally managed by parents.
“More broadly, however, it is of critical importance that young people develop their own skill set for their use of all forms of media.”