I think its mainly a mix of two factors. One factor is that many young people today suffer from what Durkheim called "anomie" (social instability resulting fro

I think its mainly a mix of two factors. One factor is that many young people today suffer from what Durkheim called "anomie" (social instability resulting from a breakdown of standards and values) on a personal level. They feel rudderless, lost and hopeless about the future (economically, environmentally, politically). These feelings manifest themselves as a what they perceive as a physical ailment. Though no tangible, physical symptoms exist this malady feels very real to the suffering young person. The other is the social factor. Social contagion leads young people to take their cues from other young people, many of whom suffer from similar issues. They are encouraged from their peers across social media to embrace their condition (there's no shame in being sick!). In addition to this encouragement, having an illness or a disability grants an individual a certain amount of status in the grievance culture that is currently en vogue among large swathes of the population (very similar to being part of a "marginalized group"). It creates a feeling of belonging and acceptance by others who also suffer from these invisible maladies - a feeling of belonging and acceptance that is often never otherwise found in the lives of these young people.