I feel the same as you, and after reading the article, it doesn't really prove the strong claims in the title. At least not as a factual conclusion. There is corelation, but the article points out that it is not causation.
“It’s unclear, based on these data, whether AI use is contributing to poor mental health and well-being, or whether students who are already in distress in certain ways are more likely to turn to AI,” Anderson said.
It's ironic in a way, since one of the dangerous things that drives people to AI is how it confirms a person's bias.