Cornell study – What does the scholarly research say about the effect of gender transition on transgender well-being?
Update on the Biology of Transgender Identity
[everything you wanted to know about the science of gender variance – and actually readable]
Myths About Transition Regrets [This article links to a number of papers evidencing good outcomes for people who transition]
Trans Suicide – a Guardian article reporting on trans suicide statistics.
Canadian Study – demonstrating support of trans people improves mental health
A Reddit thread here lists a number of references that demonstrate the effectiveness of transition to improve mental health