On TikTok, the hashtag "highfunctioninganxiety" has almost 180 million views. And while the idea isn't new, the pervasiveness of the term is.

"High-functioning" isn't clinically defined, says John T. Maier, a psychotherapist in Cambridge Massachusetts, but generally it refers to those who perform well in work or in school. So if someone has high-functioning anxiety, it means they are excelling at their job, despite being in poor mental health.