The scientific value of RCTs is severely impeded when studying the impact of gender-affirming care on the mental health of trans adolescent. Gender-affirming interventions have physiologically evident effects and are highly desired by participants, giving rise to concerns over adherence, drop-out, response bias, and generalizability. Complementary and well-designed observational studies can instead be used to ground reliable recommendations for clinical practice and policymaking in adolescent trans healthcare, without the need for RCTs.