Exploring biological factors in gender identity formation [not sex]: Integrating biopsychosocial perspectives

Objective: To explore the influence of biological networks on cognition, emotion, and gender identity. Methods: We conducted an extensive mixed-methods review, synthesizing of existing literature and research from neurobiology, endocrinology, evolutionary psychology, and sociology, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Confidence in the Evidence from Reviews of Qualitative Research (CERQual) guidelines to assess neurobiological factors in gender identity versus sex. Results: Early hormonal exposure shapes brain development and behaviors, such as systemizing, empathy, and aggressive tendencies, influencing gender identity beyond biological sex. Conclusions: Biological factors can strongly shape gender identity, sometimes independently of physical sex, alongside cultural influences.