The Cass Review Needs to be Thrown Out Entirely. This is Why.

This article was written by Rowan, Milo and Luci from Glasgow and edited by Kai and Ashleigh, with scientific advice provided by Dr Cora Sargeant.

The final Cass Report has been out for less than a week, and already several groups such as Trans Actual[1], Trans Safety Network[2], and Transgender Action Bloc[3] have issued statements pointing out its worrying implications and shaky grounding. And now instead of talking about how the NHS has failed and is still failing trans children through long waiting lists and a lack of certainty, we have to talk about this review which failed to meaningfully address any of those issues.

Our aim here is not to outline the contents of the report in full. Others have produced summaries and highlighted major takeaways, such as in these articles by PinkNews[4] and the Guardian[5]. There has also been reporting on the flawed methodologies[6] underpinning the report’s supplementary research, and how the people involved[7] in conducting the research may have biassed its conclusions. Unfortunately this report has huge implications for what the NHS is going to do next, and what life will be like for trans people, especially children and young people, in the coming years.

We contend that the Cass Review is not fit for purpose. We suggest that it was not merely knocked off course by a flawed methodology. We believe the Cass Report is a deliberate part of a political project aiming to reduce the availability of trans healthcare, possibly eventually in its entirety. It is imperative that we understand this and act on it. The people who made it happen and are taking action based on it must be held accountable. For all these reasons, we believe the Cass Report must be thrown out entirely.

An ‘Independent Review’

The Cass Report has completely failed in its remit as an independent review. The research underpinning the review and its conclusions has fundamental flaws in its methodology which have led it to exclude a huge swathe of the relevant evidence and experience that exists in the field of trans healthcare. The review also has connections to prominent anti-trans figures and groups at a variety of levels, including conversion therapy advocates, who seem to have influenced the report from its rhetoric down to the design of its research

Failures of Methodology

A Biassed Approach

Before the final report had even been published, criticisms had already arisen[6] in academic spaces of the poor research practices and inbuilt biases of the Cass Review. The content of the final report only strengthens these concerns. The primary research carried out to support the review was a set of systematic reviews of existing research, carried out within the Trials Unit at the University of York. These have been published in the British Medical Journal (BMJ) and are summarised in the appendices of the final report.

The purpose of a systematic review within fields such as social policy and medicine is to gather a broad understanding of existing research in order to build a picture of the overall trends within the field and identify areas where there is a lack of research. As part of this it is common to use various metrics to give a general guide to which research is of better or worse quality in order to give more or less weight to various trends. What is not common practice in comparable cases is to use these metrics to eliminate most existing literature from consideration, which is exactly what the University of York did.

In taking this approach, the systematic review of care guidelines recommends just two guidelines for consideration by the Cass Review (the recent Swedish and Finnish guidelines which the final report seems deeply enamoured with), which has already gained them some criticism from other health bodies[8]. A similar approach was taken with the systematic reviews of puberty blockers and hormone replacement therapy, likewise eliminating many studies from consideration on the basis of not meeting the quality criteria for the review.

Studies may be considered of lower quality for all sorts of reasons that have nothing to do with data quality, including the way the results have been written up or because of a smaller sample size (which is common across trans healthcare research due to the small overall trans population and the even smaller population who have access to blockers or hormones through official medical channels). 

The researchers are open about using a methodology that prioritises randomised controlled trials. In a randomised control trial participants receive a random treatment: either the medication (e.g. puberty blocker) or a placebo. This research method has been considered inappropriate for trans healthcare[9] , given the harms of essentially withholding treatment from the control group, and the fact that withheld care in this case does not provide a neutral baseline with which to compare results.

Many areas of medicine face these issues, and as a result rely on multiple kinds of research to form a basis for treatment guidelines. The systematic review heavily disfavours guidelines and research based on expert opinion, as well as observational studies.[10] This is used to exclude widely respected professional best practice such as the WPATH guidelines (which are informed by observational studies), as well as guidelines that base their practice on WPATH’s recommendations.

The use of such an high bar for evidence–unusual outside of drug development trials–would generally call for a specific methodological justification, especially in a case where there is not a large amount of existing research in the field and where the research being carried out is not involved in the creation of any kind of new clinical practice. This enormous thinning down of the available evidence is compounded by the refusal to consider any literature not originally published in English. While this might be an understandable consideration in a less well-resourced piece of work, this seems like sheer laziness in the case of a state-supported research programme designed to aid policy making.

This methodology means that the Cass Review has failed to even consider a huge volume of the existing literature on trans healthcare and has biassed itself towards a specific and unusual subset of the existing data that is unrepresentative of the field as a whole. Given that the final report often uses the Uni of York systematic reviews to argue that there is “insufficient evidence” to support current clinical practice (for example around the use of puberty blockers or an affirmative approach to social transition), it seems fatal to the validity of the report’s conclusions that the key supporting academic work is so flawed.

Poor-Quality Evidence

Despite the incredibly strict requirements for existing research to be considered in the systematic reviews, the final report trades freely in citations of poor quality or/and politically motivated work, and even incorrectly cites literature in order to support their desired outcome.

The report repeatedly cites Ken Zucker (1985)[11] to support its assertions about the number of people who regret transition. Zucker is widely known for his heavily criticised claim that 80% of young people ‘desist’ from being trans, as well as his use of practices likened to conversion therapy. They back this up with Thomas Steensma’s (2013)[12] study on factors associated with desistance and persistence. Steensma has clarified publicly that the study should not be used to calculate rates of persistence or desistance[13], as its research design (aimed at studying characteristics of persisting trans patients) risks inflating the number of desisters. The Cass Report uses it to do just this several times.

Other citations Cass relies on around desistance and detransition are also highly suspect. The report relies on work by Lisa Littman–best known for her widely discredited theory of ‘rapid onset gender dysphoria’[14]–to provide information about detransition, which they support with a 2022 study by Eva van den Bussche[15] which sourced its participants from r/detrans (a highly politicised reddit forum, in which only 44% of users are actually detransitioned[16]), private Facebook groups, and a detransition forum called Post Trans. Given that these spaces typically attract the most militantly political (and frequently transphobic[17]) desisters and detransitioners, this is hardly a representative study.

The Uni of York research also makes questionable interpretations of some of the studies that are included in their systematic reviews. Among other examples, the reviewers neglect to mention that a study by Turban et al (2021)[18] adjusted for experiences of transphobic bullying in school when comparing outcomes for those socially transitioning as children and as adults and found no difference. The York review only notes the unadjusted result, in which those who transitioned as children had worse outcomes. They then use this misinterpretation to suggest that there is inconsistent evidence of the benefits of social transition, which is the assertion that many of Cass’ policy recommendations rest on.

Notably underrepresented in the report are trans people ourselves. The main qualitative study of service users by the Uni of York team consulted just 32 trans people: 14 current GIDS service users and 18 young adults who had previously accessed NHS youth gender services[19]. Four of the current service users had accessed any endocrine care (i.e. puberty blockers or hormone therapy). Thirty-two interviews, each 60-90 minutes, is not a great quantity of data for the scale of a national service, but could nevertheless be informative if analysed and presented carefully. The report does not do this. Participants are only referred to abstractly (“some young people said”) and there is no effort to provide information about who made which comments (e.g. whether a comment was from someone who had experienced endocrine treatment, whether a comment was from a participant who detransitioned), or to correlate sentiments across participants, or to provide any indication of the frequency of a given viewpoint or sentiment.

This makes the qualitative data indistinguishable from simple anecdotal evidence. It is impossible to tell from the way this research is used in the body of the report to what degree Cass is cherry-picking quotes that support the conclusions she has reached, or if the findings she presents in any way reflect the views expressed by the limited pool of participants. This cannot be checked by comparing to the original research paper because it has not been published, despite the study protocol on the Cass Review’s website stating that there would be an academic paper[20]. Karl Atkin, the Chief Investigator for this specific piece of research, appears to have no published papers even remotely related[21] at the time of writing. It seems highly likely that the reason that this research does not appear to be published in a journal (as the systematic reviews are) is that it comes nowhere near to achieving publishable quality in supporting the conclusions Cass uses it to evidence.

These highly selective, inconsistent research practices suggest an approach to the literature motivated by finding any way to support conclusions that the Cass Review had already decided on rather than the balanced, independent review that was supposed to take place. Given the statements Hilary Cass has made since the publication of the report (such as publicly expressing concern that a conversion therapy ban would make it hard for clinicians to do their job[22]), it seems incredibly likely that this report was constructed, from its methodology to its citations, to act as legitimation for anti-trans sentiment and practices in healthcare.

Connections to Anti-Trans Groups

While trans people have had little input into the report, anti-trans groups and people within the medical sphere seem to have had a great deal of influence. We have found a number of connections between the Cass Review and its supporting research, and anti-trans groups and conversion therapy advocates.

One of the key researchers associated with the Uni of York group is Trilby Langton (who often goes by Tilly). Langton was a clinician with Tavistock, but at some point left the service, becoming increasingly involved in anti-trans medical circles. She is credited as contributing to “the conception of the review” on all of the systematic reviews. She is the only person on the credited author list of any of these papers with a background in gender-related care, meaning that she was almost certainly relied upon for her knowledge and opinions of the field.

In 2022, Langton was part of a group called Explore Consultation (and possibly still is, they do not have a public presence so we cannot confirm either way), who provided training to NHS Trusts in “Gender Exploratory Therapy”[23], a practice which amounts to a rebranding of conversion therapy[24]. In a training session provided to Lambeth CAMHS in 2022, the consultancy promoted transphobic pressure group Transgender Trend, among others, to NHS staff. Langton is one of five named members of Explore Consultation, a list that also includes Anastassis Spiliadis and Dr Anna Hutchinson.

Spiliadis coined the term Gender Exploratory Therapy in 2019 (according to his website[25]), is a board member of the anti-trans Society for Evidence-based Gender Medicine (SEGM), and has links to anti-trans organisation Genspect, as does Dr Hutchinson who was a speaker at this year’s ‘First Do No Harm’ conference organised by the transphobic Clinical Advisory Group on Sex and Gender (CAN-SG). Hutchinson and Spiliadis were two of the initial whistleblowers against Tavistock[26] whose complaints ultimately resulted in the Cass Review being commissioned. Hutchinson has now been appointed as[27] an Education Lead for the new National Children & Young People’s Gender Dysphoria Service training programme, allowing her to shape the successor to the current GIDS.

Langton, Hutchinson, and Spiliadis all met with Kemi Badenoch on 16th June 2021 (at the time Parliamentary Under-Secretary for Equalities, now Minister for Women and Equalities), according to the Treasury Minister’s Meetings transparency document[28], to ‘discuss how the proposed Conversion Therapy Bill will effect [sic] young people questioning their gender’, a cause which Hilary Cass has now publicly taken up, as mentioned above. This was around the time (perhaps shortly before) Langton joined the Uni of York research group.

Given that the conclusions of the report–especially in its favouring of a purely psychiatric approach to trans care and its hostility to the affirmative model–seem to be pushing for a Gender Exploratory Therapy approach, it is difficult not to suspect that Langton (and by proxy her colleagues at Explore Consultation) have had some impact on the outcome of the review. Certainly the systematic reviews that she helped to design specifically eliminate from consideration almost all existing evidence and best practice that disagrees with her approach, and significantly favours the new Finnish and Swedish models which are the closest to Gender Exploratory Therapy methods.

Hilary Cass herself also has connections to the international anti-trans movement, which seem to have been in part facilitated by Riittakerttu Kaltiala, who oversaw the establishment of the Finnish adolescent gender service (which the Cass Report is highly enthusiastic about). The service that Kaltiala set up has been the subject of truly horrifying reports of malpractice and abuse[29], which it has dismissed by claiming such practices are a necessary part of their clinical process. Kaltiala also gave the keynote speech at the same CAN-SG conference that Dr Hutchinson spoke at, placing her in the same anti-trans circles as Hutchinson, Langton, and Spiliadis.

Kaltiala disclosed in a recent research paper that she was appointed to an advisory role[30] for the Cass Review. Who the other advisors are has not been disclosed: it seems likely that this conflict of interest disclosure has accidentally revealed what was supposed to be an anonymous, confidential role, which would have masked her involvement in the review. It also seems that Kaltiala was keen to introduce Hilary Cass to Patrick Hunter[31], a member of SEGM and the Catholic Medical Association (CMA), and indeed they did meet over video call after Kaltiala’s introduction. Hunter was appointed to the Florida Board of Health by Ron DeSantis and was instrumental in bringing about the Florida bill to ban trans healthcare, partly through arranging for a slew of ‘evidence’ to be submitted by SEGM members.

When citing a recording from the WPATH 2016 conference, Cass uses a YouTube channel called Thoughts on Things and Stuff. This appears to be the associated channel of a now-defunct blog largely focussed on criticising the Mormon Church. Why this was relevant to Cass is unclear, although titles of recent uploads at the time of the WPATH video include “Dr. Stephen Levine: 13 Untruths Behind Gender Affirmative Therapies for Kids” (Levine is an advisor to Genspect) and “Gays Against Groomers: stop the indoctrination and medicalization of children. 2023 Florida testimony.”, which perhaps provides a clue to how Hilary Cass ended up citing a channel with only 22.4K subscribers. It thus seems that, in addition to being advised by and networked with a variety of prominent anti-trans figures and organisations, Hilary Cass appears to be getting her professional news from homophobic and transphobic YouTube channels. 


The poorly-designed methodology and selectively-used citations of the Cass Report are enough on their own to seriously call into question the validity of any of the report’s conclusions and render it a poor basis upon which to advocate for a complete transformation of a clinical field. In combination with the array of connections we have found between those working on the review at all levels and transphobic and conversion therapy groups, it is impossible to ignore the evidence suggesting that these deficiencies are a deliberate part of a review that was always designed to undermine the autonomy of trans children, pathologise transness, and restrict access to medical care.

The report advocates throughout its text for an approach largely modelled on the new Finnish approach–designed by review advisor Kaltiala–which has, as mentioned, had reports of horrific results for the children subjected to it. The psychiatrisation and rejection of affirmative approaches, along with the pathologisation of transness perpetuated throughout the report, align closely with the ‘Gender Exploratory Therapy’ conversion practices promoted by Trilby Langton and her associates. 

While we found or had reported to us many problems with the underlying work and methodology of the Cass Report and overall review process, we by no means believe that what we’ve presented here is a comprehensive list. We are a small team without any major academic or institutional resources behind us: it is almost certain we have missed things and we expect similar issues to continue to be found as the report is scrutinised by a wider audience. Similarly, there may be further connections to anti-trans groups that we haven’t been able to uncover that will surface as more of the review process comes to light.

With Cass now expressing concerns about a conversion therapy ban, the new adolescent service implementation looking likely to restrict hormone intervention for all under-25s, and the Tavistock clinicians–the only ones in the UK with actual existing experience–increasingly pushed out of the picture, it is hard to avoid the conclusion that the Cass Review has been a political project from start to finish, intended to give transphobes free reign to reshape the healthcare of children and adults across the country.

What Happens Next?

Following the publication of the Cass Report, the focus shifts back to NHS England. It currently seems they have accepted the report as legitimate and intend to implement Cass’ recommendations into policy. John Stewart and James Palmer, the National and Medical Directors of Specialised Commissioning for NHS England respectively, sent a letter to the adult GICs in England on the 9th of April (the day before the Cass Report was published) announcing that they intend to launch a review of the operation of the GICs.[32] If the assumptions and practices of the Cass Report are allowed to go unchallenged, it seems likely that this review may continue these trends and potentially prove equally damaging.

As for the adolescent service, the Cass Report essentially recommends implementing the most restrictive version of the service outlined a few months ago in the NHS consultation[33] on the new referral pathway, with greater restriction on medical transition and a stronger focus on psychiatric treatment. This move is not set in stone: an independent review is not legally binding and NHS England could decide (for example) that the review was methodologically unsound or unduly influenced by pressure groups, but this would require significant work, advocacy and good luck on our part.

The report is clearly taking aim at the treatment of all trans people, not just children. The follow-through service for 17-25s[34] will not be intended to solve the issue of huge wait times (which are not mentioned in conjunction with the ‘concerns’ Cass raises about the adult services). The report clearly aims to heavily restrict medical transition for under-18s, and the next step is to do the same for adult services. This echoes attempts in the USA[35] to ban trans healthcare for under 25s entirely. A notable nod towards this aim is the statement that those who transition in their youth (or possibly even as young adults) ‘may have no frame of reference to cause them to regret or detransition’.[36] This makes it explicit that the review considers it a worse outcome for someone to become a happy and healthy transgender adult than an equally happy and healthy cisgender one.

It is impossible to predict exactly how the consequences of the report will play out over the coming months and years. However, it seems very likely that the anti-trans lobby, both in the UK and internationally, will attempt to build from the conclusions of the report in order to legitimise their attempts to make trans lives–especially the lives of trans children–unlivable. The extent to which this is effective will be dictated significantly by the degree to which the Cass Report is seen to be a legitimate and independent source of information and recommendations. 

We need to make it widely understood that it is not legitimate, and that we will not accept it. 

What Do We Do?

Mainstream reporting on the Cass Review is largely positive, with little commentary on its lack of credibility and the bias inherent in its design. This isn’t unexpected, but in order to prevent the changes it recommends being introduced, its reputation needs to change.

We mentioned that some of the figures involved in the design of the review have links to anti-trans groups, but several are working academics who as far as we can tell, have neutral-to-positive opinions about trans people: Jo Taylor, Catherine Elizabeth Hewitt, Lorna Fraser, Claire Heathcote, Stuart William Jarvis, Alex Mitchell, and Ruth Hall. Taylor and Hewitt in particular are experienced academics with a large number of publications to their name, with Taylor being the lead author on the majority of the systematic reviews. We would hope to see them make statements regarding the poor quality of the final papers, acknowledge whether or not they were aware of their colleagues’ existing interests with regards to the review’s outcomes, and perhaps even ask for a retraction of their name from the paper.

The research was ultimately conducted under the University of York, but fully unpicking the degree of academic and research poor practice will likely take several years to come to fruition. What can be asked now is this: why has the research paper regarding qualitative interviews with GIDS service users, parents, and clinicians not been published, contrary to the research protocol?

Karl Atkin, the chief investigator, does not appear in any other research conducted surrounding the review, so we would be curious to hear from him and the University of York about why the paper hasn’t been published, as was promised in its study protocol.[20] Longer term, we hope that all of the research commissioned within the review will be examined by health policy academics and the University of York in order to fully assess the extent of the research’s credibility (or lack thereof).

We also don’t know the full membership of the advisory board, and given the evidence there is of bias throughout the process of the review, the board membership should be made public. This could be through pressure or through an FOI request, but either way if they want to counter accusations of bias, they may as well start by being transparent about everyone who was involved.

The research was commissioned–and will be ultimately acted upon–by NHS England. The letter they sent to the adult GICs was signed by John Stewart and Professor James Palmer, National Director and Medical Director of Specialised Commissioning by NHS England respectively. They are the very top of the chain; realistically the best way to resist the report’s recommendations being implemented is going to be through workplace organising by NHS staff. That means as many people as possible need to know about the report and the shoddy research basis. Given the current environment, it’s hardly surprising that only 34% of trans NHS staff are completely open about their identity in the workplace[37]. LGBT+ Staff Networks will be an important means of communication, and unions like the BMA and RCN need to take up strong positions in support of their trans colleagues. 

If you know someone who works in the NHS or you yourself work in the NHS, talk to people about it. Tell them why the research is poorly conducted, and what the outcomes for trans people will be. Take it to your local union branch. 

Not only does it need to be widely understood that this report lacks credibility and is clearly aimed at harming trans people, people need to show that they won’t stand for NHS policy to be dictated by it. That might be a union branch motion refusing to go along with recommendations that have been poorly researched, or it might be an email campaign to your local MP or local authority Director of Public Health. Trans Actual are already starting to co-ordinate organised action, and local groups have already done actions such as banner drops. Get involved and get loud.


  6. Horton, C. (2024). The Cass Review: Cis-supremacy in the UK’s approach to healthcare for trans children. International Journal of Transgender Health, 1–25.
  9. Ashley, F., Tordoff, D. M., Olson-Kennedy, J., & Restar, A. J. (2023). Randomized-controlled trials are methodologically inappropriate in adolescent transgender healthcare. International Journal of Transgender Health, 1–12.
  10. Cass Report, p. 55
  11. Zucker, K. J. (1985). Cross-gender-identified children. Gender Dysphoria, 75-174.
  12. Steensma TD, McGuire JK, Kreukels BP, Beekman AJ, Cohen-Kettenis PT. Factors associated with desistence and persistence of childhood gender dysphoria: a quantitative follow-up study. J Am Acad Child Adolesc Psychiatry. 2013 Jun;52(6):582-90. doi: 10.1016/j.jaac.2013.03.016. Epub 2013 May 3. PMID: 23702447.
  14. Bauer, G. R., Lawson, M. L., Metzger, D. L., & Trans Youth CAN! Research Team (2022). Do Clinical Data from Transgender Adolescents Support the Phenomenon of “Rapid Onset Gender Dysphoria”?. The Journal of pediatrics, 243, 224–227.e2.
  15. Vandenbussche, E. (2022). Detransition-Related Needs and Support: A Cross-Sectional Online Survey. Journal of Homosexuality, 69(9), 1602–1620.
  18. Turban JL, King D, Li JJ, et al. Timing of social transition for transgender and gender diverse youth, K-12 harassment, and adult mental health outcomes. J Adolesc Health 2021;69:991–8. doi:10.1016/j.jadohealth.2021.06.001
  19. Cass Report, Appendix 3
  24. Ashley, F. (2023). Interrogating Gender-Exploratory Therapy. Perspectives on Psychological Science, 18(2), 472-481.
  29. (content warning for medicalised abuse of children. Article in Finnish; an English summary can be found in this Twitter thread:
  34.  Cass Report, Recommendation 23
  36. Cass Report, p. 195
  37. GLADD and BMA (2016) Sexual orientation and gender identity in the medical profession.