Home › Research › Cass Review

Cass Review: what the English review of youth gender care concludes (NHS, 2024)

The Cass Review is an independent review of care for children and young people with gender dysphoria in England, led by paediatrician Hilary Cass. In her foreword, Cass writes that this is an area of "remarkably weak evidence" and that study results are exaggerated or misrepresented by people on all sides of the debate. According to her, there is no good evidence on the long-term outcomes of treatments.

Commission and method

NHS England commissioned the Review in autumn 2020. An interim report appeared in 2022, the final report in April 2024. The research programme included eight systematic reviews by the University of York — on puberty blockers, cross-sex hormones, social transition and guidelines, among others — and an international survey of clinics (table 1 of the report). The York researchers assessed the studies with an adapted version of the Newcastle-Ottawa scale, under which a study can count as high quality even without randomisation (source).

Of the 50 studies on puberty suppression, one was of high quality, 25 of moderate and 24 of low quality; of the 53 studies on hormones, one was high, 33 moderate and 19 low (blockers, hormones). A review of guidelines (AGREE II) gave the Swedish guideline 71 percent for rigour of development, the Finnish 51 percent, WPATH 2022 35 percent and the Norwegian 2020 guideline 30 percent; the Cass Review names the Swedish and Finnish guidelines as the only two that could be recommended for use in practice (source).

Main conclusions

• Puberty blockers: no changes in gender dysphoria or body satisfaction demonstrated; insufficient or inconsistent evidence on psychological wellbeing; because nearly all young people go on to hormones, there is no evidence that blockers buy time to think (paras 81 to 83 of the summary; source).
• Cross-sex hormones: no conclusions possible on the effect on gender dysphoria, psychosocial health or fertility; suggestive evidence that psychological health may improve; the evidence does not support the claim that hormones reduce suicide risk (paras 85 and 86).
• Social transition: the review found no clear evidence that social transition in childhood has positive or negative mental health outcomes; those who transitioned socially earlier were more likely to proceed to a medical pathway (para 76). See also desistance research.
• Co-occurring problems: in the clinics studied, on average 9 percent (range 0 to 26 percent) of referred young people had an autism diagnosis and 10 percent ADHD (para 5.40, table 3). The report advises that co-occurring mental health problems are also treated. See Cass on co-occurring conditions.
• According to the Review, puberty blockers should be offered only within a research protocol (para 84), and hormones from age 16 only with extreme caution (recommendation 8).

Consequences in England

The NHS stopped routinely prescribing puberty blockers to minors in March 2024; in December 2024 the UK government made the ban on supply via private prescribers indefinite (source). The Tavistock clinic (GIDS) closed on 31 March 2024; NHS England calls this one of the steps following the 2022 interim report (source). Earlier, Sweden (SBU and Socialstyrelsen 2022) and Norway (Ukom 2023) had also arrived at cautious advice, and Finland described psychosocial care as the first treatment in 2020; Denmark follows a more cautious policy.

Reactions and criticism

There is also expert criticism of the method of the reviews. Noone and colleagues (2025) saw a high risk of bias in each of the seven systematic reviews they assessed (source). The Yale Integrity Project argued that the emphasis on high-quality evidence is inappropriate, because much care in other parts of medicine also rests on moderate or low-quality evidence (source). See also the WPATH Files and the versions of the WPATH SOC.

What this means for the Netherlands

In a letter of 4 June 2024, the minister wrote that the Cass Review identifies significant differences between the Dutch approach and the way the Tavistock clinic worked, and informed Parliament of the commission to the Health Council (source). In its advice of 30 June 2026, the Health Council called the strength of evidence low to very low, described Dutch care as carefully organised and wrote that the English literature does not apply to the Dutch situation without qualification (source). See also the Dutch Protocol, the VUmc protocol and the Dutch rollout.