What the studies show

The evidence is most reliable for short-term complications. A systematic review of 39 mastectomy studies in people under 26 rated only complication outcomes as high certainty: no deaths, about 20 per 1,000 losing the nipple or graft, and about 50 per 1,000 with thick scarring (Miroshnychenko et al., 2024). In 209 adolescents at Kaiser Permanente, 7.3% of those followed for a year had a surgical complication and 10.9% needed revision, as the operation rate rose about 13-fold (Tang et al., 2022). For vaginoplasty, 26 mostly low-quality case series found stenosis the most common complication, and only one study measured quality of life (Horbach et al., 2015). Gender distress, mental health, suicide and quality of life were rated weak or very weak evidence, though one study suggested roughly halved non-suicidal self-harm after mastectomy (Miroshnychenko et al., 2024).

Long-term mental health data are sparse and contested. A Swedish registry study initially linked each year since surgery to 8% lower odds of mental health treatment, but a 2020 correction found no advantage compared with diagnosed people who did not have surgery (Bränström & Pachankis, 2020; Society for Evidence-Based Gender Medicine, 2020). An earlier Swedish cohort of 324 people found suicide deaths about 19 times higher than the general population, based on 10 deaths, but had no untreated comparison group (Dhejne et al., 2011). Reported regret is generally low: about 1% pooled across 27 studies (Bustos et al., 2021), 2.2% formal legal reversals in Sweden, typically about 8 years after transition (Dhejne et al., 2014), and 0.95% recorded in adolescent chart notes (Tang et al., 2022). Regret over fertility choices after reproductive-organ removal was much more common, at 39% (Johnson et al., 2024).

Limits of the evidence

Almost no study compares operated patients with similar unoperated people, so benefit cannot be estimated. Regret estimates rest on short follow-up, heavy attrition (36% in the largest study pooled by Bustos et al., 2021), narrow definitions, and surgeon-run surveys with low response (Narayan et al., 2021; Bruce et al., 2023). Most data come from adults treated under older, stricter protocols. Breastfeeding loss after mastectomy is documented only in a single case report (Gribble et al., 2023). Many studies come from teams who perform these operations.