TikTok especially is full of videos of sad, pretty girls who self-harm and I DO think it's being glamorised as are a plethora of other mental health problems.
I think there is something here about valid ways of displaying distress, as well as what are considered legitimate reasons for emotional distress in teenage girls.
It's said a lot on this board that being a teenage girl is pretty grim - unwanted sexual attention, menstruation, potentially having your life and freedom curtailed hugely compared with teenage boys. On top of that, many girls may be experiencing difficult or traumatic things, like bereavement, parental divorce, abuse or neglect.
All of those things are hard to talk about and to articulate even for adults, let alone teenagers. And in a group of friends teens can feel like they are the only one who has something big going on in their life, while everyone else is obsessed with boys and selfie filters (even if lots of people in the peer group are feeling the same on the inside).
On top of that again, I think there is a big push in parenting to try to shield children from anything negative, with the implicit expectation that children should be happy all the time. I think that can mean that teaching emotional intelligence - recognising and articulating emotions, sitting with sadness and anger without being overwhelmed - can be completely neglected. So when teenagers experience difficult complex feelings and difficult complex situations, they can really struggle to manage.
I also think we all learn from society about what are culturally acceptable ways and reasons to be unhappy. If there are lots of articles about tragic deaths from anorexia, alongside arty pictures of soulful emaciated girls with perfect makeup; or Instagram / Tiktok videos about self harm are getting loads of supportive messages about how brave and strong they are; what we learn is that these are the ways that distress is recognised. This is particularly important for teenage girls, who may have internalised the message that they need to discount their feelings in favour of others and who may potentially believe that distress is only valid if it is recognised by others.
There's a book called "Crazy like us" by Ethan Waters, which explores this idea of a culturally localised "symptom pool" that changes over time. It feels to me like anorexia, self-harm, maybe binge eating, along with the associated narratives, are available to women and girls in the UK as ways of expressing, explaining and managing complex emotional distress in a culturally accepted and understood manner.