It's this study. You'll recognise Prof Kaltiala's name from the upcoming conference.
Ruuska S, Tuisku K, Holttinen T, et alAll-cause and suicide mortalities among adolescents and young adults who contacted specialised gender identity services in Finland in 1996–2019: a register studyBMJ Ment Health 2024;27:e300940.
https://mentalhealth.bmj.com/content/27/1/e300940.full
https://can-sg.org/can-sg-conference/
Quick scamper, more later, indicates a robust cohort study with a thoughtfully selected comparator group for the analysis.
Four male and four female controls matched for age and municipality of birth were extracted from the Population Information System for each gender-referred individual. The gender-referred individual’s index date was assigned to all controls. [My emphasis.]
Sensible variables and corrections. E.g., the number of "psychiatric treatment contacts" for the referred young people and those in the comparator.
When only registered sex and year of birth were controlled for, the HR for suicide mortality greatly increased in the gender-referred group. However, when the number of specialist-level psychiatric treatment contacts was added to the model, the difference between cases and controls levelled out. Death by suicide was significantly predicted by a high number of psychiatric treatment contacts, and borderline significantly predicted by male sex and earlier birth year.
More later but it's looking methodologically sound.