Estrogen (oestrogen) treatment is linked to a significantly large increase in psychiatric problems.

Among gender-referred biological males who started feminising hormones (oestrogen), the need for specialist psychiatric care rose from 9.8% before treatment to 60.7% afterwards, the largest increase observed in the study. This worsening occurred alongside medical transition and was more pronounced than among biological females who started masculinising hormones (testosterone).

Ruuska, S.-M., Tuisku, K., Holttinen, T., and Kaltiala, R. (2026). “Psychiatric Morbidity Among Adolescents and Young Adults Who Contacted Specialised Gender Identity Services in Finland in 1996–2019: A Register Study,” Acta Paediatrica: 1–9. https://doi.org/10.1111/apa.70533.