I think this is true, and not just for transgender, on tumblr it's all about being special and being the most special of the snowflakes, I think a lot of young impressionable teenage girls go on that site being relatively ok, but then they start reading shit online, they internalize it, they see someone talk about their mental illness and they associate with it, and before you know it becomes a self fulfilling prophecy, same with when they see transgenders talk, they do realize that when a transgender posts something on tumblr they will always get tons of support simply for being transgender, otherkin is another good example, from a psychological point of view you would be deemed psychotic if you identify as another animal or be divinekin or demonkin and whatever the hell they come up with it, but these people aren't really any of that because that would mean they are psychotic, they just see people talk about it, they think "hey that sounds like me, I also REALLY like wolfs" , maybe i'm wolfkin and they see someone getting attention for it so they subconsciously adopt it too  I personally find tumblr one of the worst things to happen in modern era for mental health, so many young impressionable teens go on there actually developing more problems than they even had (you know the usual troubles a teen goes through) and eventually all the things they read become so internalized they actually become reality for them