https://www.sciencedaily.com/releases/2018/08/180822150809.htm

Among the noteworthy patterns Littman found in the survey data: 21 percent of parents reported their child had one or more friends become transgender-identified at around the same time; 20 percent reported an increase in their child's social media use around the same time as experiencing gender dysphoria symptoms; and 45 percent reported both.

The pattern of clusters of teens in friend groups becoming transgender-identified, the group dynamics of these friend groups and the types of advice viewed online led her to the hypothesis that friends and online sources could spread certain beliefs. Examples include the belief that non-specific symptoms such as feeling uncomfortable in their own skins or feeling like they don't fit in -- which could be a part of normal puberty or associated with trauma -- should be perceived as gender dysphoria; the belief that the only path to happiness is transition; and the belief that anyone who disagrees with the teen is transphobic and should be cut out of their life.