TikTok has become Gen Z’s go-to therapist. But when viral trends replace professional diagnosis, the consequences can be dangerous.

In less than a month, TikTok could have one or a few new owners, be banned again, or simply receive another reprieve to continue operating in the United States.

Fresh off a brief U.S. ban and amidst ongoing legal drama related to allegedly fueling a youth mental-health crisis, TikTok ...