Evaluations › Cass Review · Last reviewed 2026-05-16

Cass Review (2024) — full summary

Cass H. Independent Review of Gender Identity Services for Children and Young People: Final Report. NHS England, April 2024 — 388 pages, plus 9 independent systematic reviews carried out by the University of York. See also Hilary Cass in the people register and the entry in the timeline 2024-04.

1. Commission and methodology

NHS England commissioned paediatrician Dr Hilary Cass OBE in September 2020 to conduct an independent review. The methodology included:

• Nine independent systematic reviews by the University of York.
• International policy comparison (16 countries) — see comparative table.
• Qualitative research with patients, parents, professionals and detransitioners.
• Statistical analysis of GIDS cohort data.
• Consultation with clinicians, policymakers and advocacy organisations.

2. Main conclusions

• The evidence base for GnRHa is "very low certainty" (GRADE).
• Claimed effects on mental wellbeing are not confirmed by follow-up studies.
• The current adolescent referral population differs substantially from the original Dutch cohort.
• Clinical assessment should start with a holistic evaluation, not with identity affirmation as the starting point.

3. Recommendations (selection)

• GnRHa treatment only within a research setting with independent data collection.
• CSH treatment under 16 to be cautious and subject to multidisciplinary assessment.
• Routine assessment of comorbid conditions (ASD, ADHD, trauma, eating disorder).
• Regional service delivery instead of one centralised clinic.
• National follow-up system for outcomes.

4. Response from the academic community

The Cass Review was endorsed by, among others, the Royal College of Paediatrics and Child Health (RCPCH), the Royal College of Psychiatrists and the Association of Clinical Psychologists UK. Criticism came from, among others, Yale Law School (statement March 2025) and WPATH; this criticism is addressed by the Review authors in a follow-up response.¹

5. Policy consequences

NHS England withdrew standard funding for GnRHa in gender dysphoria in March 2024. Scotland and Wales announced comparable measures. Internationally, Norway (Ukom) and the state of Tennessee (US v Skrmetti) explicitly referenced the Cass Review findings.