Okay finally a source. But the thing is, there is just as much, if not more, proof that proves the opposite.
With a couple google searches I found these.
https://www.scientificamerican.com/article/what-the-science-on-gender-affirming-care-for-transgender-kids-really-shows/
This one is about how the research proves that it helps them.
https://www.washingtonpost.com/business/trans-teens-benefit-from-gender-affirming-care/2023/01/20/955f807c-98bd-11ed-a173-61e055ec24ef_story.html
https://www.statnews.com/2023/01/18/mental-health-benefits-of-gender-affirming-hormones-for-teens-persist-two-years/
These two are about how it benefits them.
https://www.theguardian.com/society/2023/mar/24/majority-trans-adults-happier-transitioning-survey
https://whatweknow.inequality.cornell.edu/topics/lgbt-equality/what-does-the-scholarly-research-say-about-the-well-being-of-transgender-people/
These two are not about Youth specifically but I thought I'd include them since they prove that it helps them generally mentally.
All of this found with a total of 3 google searches. But y'all cling to anything proving you right