Several systematic reviews of the existing literature (including the latest that was part of the series of systematic reviews commissioned by the Cass Review in the UK [Taylor, et al., 2024]) have shown estrogen in natal males does not help with their psychosocial outlook. Several systematic reviews of the existing literature have shown a wide range of problems: a lack of randomized prospective trial design, small sample sizes, recruitment biases, short duration of subject follow-up, high dropout rates, psychometrically inadequate measurement instruments, uncontrolled confounding, and lack of appropriate controls.

The first (and, to date, only) clinical study (i.e., a study that recruits actual subjects and follows them clinically rather than rely on anonymous, online, non-probability surveys) in a US setting among adolescents that promotes CSHT failed to show any improvement in psychosocial outcomes (depression, anxiety, and life satisfaction) among "youth designated male at birth" (Chen et al., 2023). 

Estrogen also does not improve physiological outcomes, as demonstrated in recent literature in disciplines as varied as neuroscience, endocrinology, neuroendocrinology, and psychoneuroendocrinology. In fact, estrogen introduces many causes of concern. The situation becomes dramatically worse after surgery.

Chen, D., Berona, J., Chan, Y.-M., Ehrensaft, D., Garofalo, R., Hidalgo, M. A., Rosenthal, S. M., Tishelman, A. C., & Olson-Kennedy, J. (2023). Psychosocial functioning in transgender youth after 2 years of hormones. New England Journal of Medicine, 388(3), 240–250. https://doi.org/10.1056/NEJMoa2206297

Taylor, J., Mitchell, A., Hall, R., Langton, T., & Fraser, L. (2024). Masculinising and feminising hormone interventions for adolescents experiencing gender dysphoria or incongruence: A systematic review. Archives of Disease in Childhood. https://adc.bmj.com/content/early/2024/04/09/archdischild-2023-326670