TikTok has been charged by the European Commission with failing to protect users’ mental health by exposing them to a relentless stream of content that risks worsening eating disorders and anxiety in a case that strikes at its business model.

Issuing a preliminary ruling on Friday, the EU regulator said TikTok’s algorithm “can be harmful” and was leading young and vulnerable users “down rabbit holes they cannot easily escape from”.

The Chinese-owned short-video platform, which has 189 million users in the EU, was found to have failed to prevent users from being served up repetitive content on themes such as body image or isolation, which can lead to anxiety, sadness, worsen existing eating disorders or mental health problems.

Officials said their investigation focused on legal content, where a single video might not be problematic, but the cumulative effect of watching scores of them on one theme could damage users’ mental health.

TikTok’s safeguards to mitigate the risks of “rabbit-hole effects” – where users are served narrow and repetitive content to keep them engaged – were found to be ineffective. For example, officials said, if a user checked a “not interested” button on a video about eating patterns, the algorithm would still offer them similar content on diet and body image. Similarly, refreshing a feed only provided a brief respite from a stream of content on one topic, it found.

“Every time a user scrolls or likes a video on TikTok, the algorithm serves more of the same leading users down rabbit holes they cannot easily escape from,” the European Commission’s lead official on tech policy, Henna Virkkunen, said. “TikTok needs to step up its efforts to protect users’ wellbeing, including those of minors.”

TikTok has been contacted for comment.

The investigation strikes at TikTok’s business model, which is built on keeping users scrolling as long as possible.

EU officials want TikTok to change the design of its ForYou feed, to give users greater control over the content they see.

“We are addressing a business model,” a commission official told reporters, saying that a business model focused mainly on engagement “can potentially create a risk” especially for minors and vulnerable adults.

The findings are part of a broader investigation launched in February 2024 under the Digital Services Act, which obliges large internet companies to take action to prevent a wide range of harms, from disinformation to damage to mental health.

The commission has already found the company violated EU rules over its “addictive design” for features such as infinite scroll. The company said at the time: “The commission’s preliminary findings present a categorically false and entirely meritless depiction of our platform” and that it would challenge the findings.

A complaint about lack of transparency over who paid for TikTok’s advertising was resolved when the company made binding commitments to change its policies last December.

TikTok, which now has a chance to examine the investigation file and mount a defence, could agree to change its recommender system to avoid a fine.

If EU officials uphold the finding, the company could be fined up to 6% of its global worldwide turnover.