This was an online survey of "Australian trans people" aged 14-25 years. The definition of trans used appears to be quite wide: "Trans is an umbrella term that includes specific gender identities, such as trans woman, trans man, genderqueer, non-binary, genderfluid or simply male or female." So it is not clear what "trans" actually means in the context of this research.
The survey selected its participants through the following methods: " The Trans Pathways online questionnaire was promoted widely through social media (namely Facebook, Twitter and Tumblr), queer departments at universities, trans and LGBTIQ support groups, parent support groups, peer-led safe spaces, various trans rights organisations in Australia, medical and mental health services, radio and by word of mouth." This means that the survey participants are a self-selected and therefore biased sample. It is not stated how the researchers prevented participants from answering the questionnaire more than once.
The report says that 859 "trans" (by the definition used in the survey) responded. The Australian Bureau of Statistics estimates that there are almost 3.82 million people aged between 14 and 25 years. The participants therefore represent 859/3815581 = 0.02% of that age range.
The participants were not balanced with respect to sex, 74% were female and 26% were male. Interestingly, while only 1.6% identified as intersex, 21% were "not sure if they are intersex".
70% reported a current diagnosis of depression, 55% reported a current diagnosis of anxiety, 11% were currently diagnosed with PTSD, 9% were currently diagnosed with a personality disorder (an interesting finding given that 20% had ever been diagnosed with a personality disorder and personality disorders don't tend to disappear), 3% had a current diagnosis of psychosis, 6% had a current eating disorder, and 23% had a current diagnosis of an autism spectrum disorder. 48% had ever been diagnosed with gender dysphoria.
48% had tried suicide, 82% reported ever having suicidal thoughts, and 91% had wanted to self harm. These results are not surprising given their negative life experiences. Suicide attempts were particularly associated with issues with accommodation (such as homelessness), experiencing school, university, or TAFE issues (not specified), experiencing bullying, experiencing neglect or been verbally or emotionally abused by a family member, physical abuse by a family member, physical abuse by someone outside of the family, sexual abuse by someone outside of the family.
With the parent respondents (separate sample) this finding is striking: "The mean age at which parents realised their young person was trans was 11 years of age. The minimum youngest age was 18 months and the maximum oldest age was 24 years old."