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The evidence pyramid in gender care

In evidence-based medicine, research is ordered in a pyramid.

The evidence pyramid

In evidence-based medicine, research is ordered in a pyramid. At the top are systematic reviews and meta-analyses of randomised controlled trials (RCTs). Beneath them are individual RCTs, prospective cohort studies, retrospective cohort studies, case-control studies, case series and finally expert opinion.

Research in gender care

In transgender care, RCTs are almost entirely absent; for practical and ethical reasons, randomisation to hormone treatment versus no hormone treatment is difficult. Most evidence comes from observational cohort studies (Amsterdam Cohort of Gender Dysphoria, the ENIGI network) and from case series.

Cass Review

The systematic reviews conducted by the University of York, which underpin the Cass Review (2024), concluded that the evidence for the effectiveness of puberty blockers and cross-sex hormones in young people is predominantly of low quality. Similar conclusions were drawn by the systematic reviews underpinning the Swedish, Finnish and Norwegian policy changes.