Another very (or perhaps not at all) interesting abstract from an article (book series chapter?) that cited that article.

From the first time individuals described a felt incongruence between their assigned and their experienced gender, people have been interested in the origins of gender dysphoria and transsexualism. This chapter focuses on the various theories and research evidence about gender identity development, which have often pointed to a biological, a psychological, or a social factor as determining one's gender identity. Over time, differing views prevailed, although the multiple perspectives also developed parallel to one another. Two distinct lines of research on gender identity development emerged: those focused on "normative" development and those focused on nonnormative or gender-variant development. The chapter first describes the multiple factors (biological, psychological, and social) that were studied in both lines of research. After that, current studies are presented that give evidence for a complex interaction of biological, psychological, and social factors in gender identity development. Recent findings from neuroimaging and genetic studies of individuals with gender dysphoria provide evidence that nature is of importance. Its exact role however remains largely enigmatic.

Regarding future studies of gender identity development, we conclude that they should week to understand not only the potential genetic and environmental (from both nature and nurture) factors, but also when these factors emerge in life and how those factors may be of influence on the full spectrum from gender-normative to gender-variant development in all its expressions.

Ah, how measured and inoffensive to everyone. This almost says nothing, almost doesn't take a stance at all. You'd have to read the entire thing to get an idea how the really feel. At least, what they're absolutely not saying is that people become transgender because they're male brains born in female bodies and vice versa.