I agree with the parallels pp have made between self harm, anorexia and now trans. All 3 are purely psychological conditions and of course are socially influenced, as they do not exist in some parts of the world (non-western parts). You certainly don’t get people in Ethiopia starving themselves or ‘feeling like’ the opposite sex ffs. Hopefully in 10 years time the ‘trend’ would have moved on from teenage girls, although will no doubt sadly be replaced by something else.
(Of course there will always be people in our society who self harm, have an ED or have gender dysmorphia, but the vast majority of teenagers who have these are doing so as part of mass hysteria and grow out of it, rather than being the ‘real deal’ imo)