I think it is more accurate to call it sex dysphoria or body dysmorphia more akin to anorexia than anything. If a person was raised alone in a vacuum would she or he have sex dysphoria, anorexia or any other body dysmorphia disorder? We'll never know for sure, but I'd bet a lot less people would.

Social contagion can increase the odds of someone developing symptoms, and culture has a big role to play as well. I do believe that the trans movement is making the problem worse by encouraging people to ruminate about it and embrace it instead of finding healthier ways of coping that don't involve life long medicalization.

So I'd say body dysmorphia disorders are definitely a real thing, but they are inextricably linked to societal influence. There is something very wrong with society when a lot of teenage girls develop anorexia. Likewise there is something horribly wrong with society if a lot of people are damaging their bodies in the pursuit of the impossible goal of changing their sex. The culture at large has catastrophically failed to accept gender nonconforming people as they are, much in the same way it has failed to accept teenage girls and women as they are.