Wow. You're right that's an amazingly badly constructed study. Low-n, indirect-non-patient self-report (parental reporting/perception bias) w/ no cross adjustment or multi-party correction. Biased recruitment practices... hecking YIKES.

Oh, and of course, the methodology was soundly criticised and contextualised in the same journal; imagine that. - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424477/

> The level of evidence produced by the Dr. Littman’s study cannot generate a new diagnostic criterion relative to the time of presentation of the demands of medical and social gender affirmation.

Surprise.