More than a dozen states and the District of Columbia filed lawsuits against TikTok on Tuesday, saying that the popular short-form video app is designed to be addictive to kids and harms their mental health.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 New York, California, Kentucky and New Jersey. All of the complaints were filed in state courts.