As the mother of two mid teen girls, I would say that the following are the main causes of social anxiety:
Social media - always on, no escape, comparing lives to others, feeling left out, beauty ideals pedalled by instagram ‘models’ that have been pumped up with lip fillers, Botox and filtered beyond recognition.
Exams - dd1 is taking 11 GCSEs and some of her peers are taking 13!! School piling on pressure through ‘motivating’ assemblies, teachers hassling them to meet target grades that were set in Y8 (thanks Progress 8 🙄) and hassling parents too (not teacher bashing, they are clearly under a lot of pressure but it’s causing mental stress to our own kids)
Openness about mental health issues. To many they are almost fashionable.
Too much choice, too much materialism, not enough spiritual growth, not enough altruism.
Not surprising kids are fucked.