There are plenty of studies that quantify depression among transgender people. The topic was SRS, because that is a treatment specifically given to alleviate gender dysphoria. But if we want to include other things like depression and various comorbid conditions, there is a plethora of research out there dissecting that topic, such as comparisons between suicide attempts - income level - homelessness - HIV status - family relations - race - etc.
Feel free to look them up.