NEW YORK — Thirteen states and the District of Columbia filed lawsuits Tuesday against TikTok, alleging the popular short-form video app is harming youth mental health by designing its platform to be addictive to kids.

The lawsuits stem from a national investigation into TikTok, which was launched in March 2022 by a bipartisan coalition of attorneys general from many states, including California, Kentucky, New Jersey and New York. All of the complaints were filed in state courts.

At the heart of each lawsuit is the TikTok algorithm, which powers what users see on the platform by populating the app’s main “For You” feed with content tailored to people’s interests. The lawsuits also emphasize design features that they say make children addicted to the platform, such as the ability to scroll endlessly through content, push notifications that come with built-in “buzzes” and face filters that create unattainable appearances for users.

In its filings, the District of Columbia called the algorithm “dopamine-inducing,” and said it was created to be intentionally addictive so the company could trap many young users into excessive use and keep them on its app for hours. TikTok does this despite knowing that these behaviors will lead to “profound psychological and physiological harms,” such as anxiety, depression, body dysmorphia and other long-lasting problems, the complaint said.

“We strongly disagree with these claims, many of which we believe to be inaccurate and misleading,” said TikTok spokesman Alex Haurek. “We’ve endeavored to work with the attorneys general for over two years, and it is incredibly disappointing they have taken this step rather than work with us on constructive solutions to industrywide challenges.”

The social media firm does not allow children under 13 to sign up for its main service and restricts some content for everyone under 18.

But Washington and several other states said in their filing that children can easily bypass those restrictions, allowing them to access the service that adults use despite the company’s claims that its platform is safe for children.

Their lawsuit also takes aim at other parts of the company’s business.

The District of Columbia alleges TikTok is operating as an “unlicensed virtual economy” by allowing people to purchase TikTok Coins — a virtual currency within the platform — and send “gifts” to streamers on TikTok LIVE who can cash them out for real money.

TikTok takes a 50% commission on these financial transactions but hasn’t registered as a money transmitter with the U.S. Treasury Department or authorities in the district, according to the complaint.

Officials say teens are frequently exploited for sexually explicit content through TikTok’s LIVE streaming feature, which has allowed the app to operate essentially as a “virtual strip club” without any age restrictions.

They also say the cut that the company gets from the financial transactions allows it to profit from exploitation.