We know that severe mental (and even physical) symptoms can "spread" in social groups (https://en.wikipedia.org/wiki/Mass_psychogenic_illness), particularly among young women who are now experiencing the sharpest rises in mental illness. There is also strong evidence that affective states (e.g. happiness or depression) spread socially, with even next-door neighbors of depressed people being significantly more likely to be depressed than those on the same block but not next-door (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3830455/).
While the TikTok Tourette's phenomenon is clearly an extreme example, it seems possible that something similar could be happening to kids constantly hearing about anxiety and depressive disorders as an immutable trait that everyone around them seems to have.
Bad metaphor - if we think of ideas spreading between people like neurons, we have increased the interconnectedness (social reach) and decreased the activation energy (removed stigma/provided language/triggered introspection).
[1] https://en.m.wikipedia.org/wiki/Ultimate_fate_of_the_univers...
The big one is “does that mean there’s more self-harm, or does that mean parents are more willing to ask for emergency help?”