Twitter users who support eating disorders often group together and form like-minded networks, sharing content that promotes eating disorder lifestyles, according to a new study.

So-called Pro-Eating Disorder (ED) communities have been documented elsewhere on the internet, "so it wasn't a huge surprise to find that Pro-ED was also active on Twitter," said lead author Alina Arseniev-Koehler of the University of Washington and Seattle Children's Research Institute.

She and her colleagues selected 45 Twitter profiles of users promoting eating disorders and examined their profiles, all their tweets, and 100 of their randomly selected followers.

The researchers found these Twitter users by searching for the hashtag #proana, which stands for "pro-anorexia.

They excluded profiles in languages other than English and of explicitly male users.

Tweets often contained Pro-ED references or language like "thighgap," "bikini bridge," "thinspo," "bonespo" and "laxies," an abbreviation for laxatives.

The researchers observed some users taking part in CalorieApril, a competition for lowest caloric intake, or the ABCdiet, "Ana Boot Camp."

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On average, about a third of users' tweets contained pro-ED references. Half of users had more than 173 followers, and all 45 profiles in total had more than 25,000 followers.

Of the nearly 4,000 followers the researchers selected to study at random, 40 percent had eating disorder references in their own profiles. As a user's ED reference tweets increased, so did their proportion of ED followers, the authors reported in the Journal of Adolescent Health.

Pro-Ana online activity "is not a new phenomenon, but it is still a concern and there is still a lot to understand about it," Arseniev-Koehler told Reuters Health by email. "Also, since the rise of social media, communities like Pro-Ana are much more public and accessible, and we see more mainstream offshoots such as Thinspiration."

It is hard to tell how much this online activity influences behavior change for people, she said.

"Such online communities could have negative influence on young people with eating disorders, so it would be important to provide educational and referral information regarding eating disorders at websites with professional input," said Kathleen Ries Merikangas of the National Institute of Mental Health in Bethesda, Maryland, who was not part of the new study.

Parents should be encouraged to make such information available to adolescents, Merikangas told Reuters Health by email.

"Pro-ED Twitter profiles tended to hold an audience of followers also interested in EDs," Arseniev-Koehler said. "But we couldn't infer how much this was driven by influence, and how much was because individuals with pre-existing Pro-ED attitudes found a like-minded community on Twitter."

"There have been efforts to censor Pro-Ana and related material on other online platforms such as Instagram and Facebook, but it's not clear how effective or helpful censorship is," Arseniev-Koehler said.

Censoring further stigmatizes people who may already be struggling with stigma surrounding EDs, who would benefit more from support than from stigma, she said.

"I think it is really important not to sensationalize Pro-ED and its potential risks," she said.

"There are also a number of Pro-Recovery and other communities with more healthful attitudes toward body image, diet and fitness, such as Proud2Bme," she said. "These are really wonderful resources to get healthful support and information."