B.P.C. Kreukels et al. (eds.), Gender Dysphoria and Disorders of Sex Development: Progress in Care and Knowledge, Focus on Sexuality Research, DOI 10.1007/978-1-4614-7441-8_2, © Springer Science+Business Media New York 2014 Abstract The development of gender identity, its variance, and gender dysphoria is thought to be a complex process involving biological and psychosocial factors. Heritabilit...