I think it's more to do with the stress of academic achievement and expectation thst a string of GCSE's at A* are necessary. In my day (mid 70s), university was the exception, a secretarial course was perfectly acceptable or a cookery course. You could enter nursing at 17 with 3/4 O'Levels. Much of it too is about our young people struggling in huge, one size fits all schools where behaviour is off the scale because exclusions aren't allowed anymore and the environment becomes highly charged.
My dd didn't much care about clothes, social media etc. She did care about noise, seeing others being bullied and being yelled at by teaching staff because she and her classmates were stupid and would fail.
The cutting started in the GCSE year. I didn't know. Largely exam stress. She went to the GP to get help when she started taking small od's as well. I was contacted. I asked for a orivate referral because the GP said CAMHS were useless and wouldn't help. She refused and told me to get help off the internet. I felt that inappropriate and insisted on a CAMHS referral. Six weeks later CAMHS closed the case after offering nadequate and inaccessible group therapy and refusing to negotiate an alternative. Dd had anxiety and depression too. CAMHS said her new school was likely to help and then offered something so badly timed it would have tamen her out for 2/3 of a day.
The inference was that the oroblem was family related. I didn't think so. I was able to appoint a consultant psychiatrist. DD tried CBT, and another counsellor, was given propranolol and fluoxetine. It helped a bit. Just before her yr12 exams she took a v small overdose and worried about herself so went to a&e to get herself checked over They wanted her to stay overnight with a 1:1 nurse at a cost of £850 to facilitate an emergency CAMHS review. She came home and saw CAMHS the follliwing Tuesday. CAMHS looked for family problems again (oh and the hospital and CAMHS reported us to SS). The nurse said she'd get counselling quickly but it didn't materialise.
The following day we saw her consultant psychiatrist who completed the ASD and ADHD assessments. DD has ADHD/ADD variant. This was the problem. She began to turn the cirner immediately.
Phoned CAMHS to tell them "well now mum, I think she's a bit old for that at 17". Their counselling eventually happened. They closed her case after the first session - whilst claiming they can't refer because it's essential they know outcomes.
It is not all about social media and looks. It is largely due to educational pressures, schools that are on the verge of lising control and the failure of child and adolescent mental health services.
My dd was lucky. We had the money for her to receive MH suppirt and care.