This report released today by the journal The New Atlantis is worth reading. It is a review of the attempts to study sexual orientation and gender identity scientifically; it also assesses the "social stress hypothesis," which posits that mental illness in the LGBT community can be entirely or largely accounted for in terms of that population's subjection to various forms of social stress: stigma, discrimination, etc.

This video provides a brief introduction.

I expect this'll be pretty controversial, but it is well worth reading. One almost thinks that it shouldn't be controversial among the scientists and social scientists studied, who often acknowledge that they have achieved provisional results that are not or are hardly statistically significant. The report also stresses the difficulty of defining and operationalizing what people want to study on these topics: "sexual orientation," "sexual desire," "gender identity," "social stress".

The report aims just at articulating what the science does and does not show on these topics. It doesn't advance its own policy solutions.

It is also of interest that, toward the beginnings of Parts 1 and 3, the report waxes philosophical on the topic of sexual orientation and gender identity.