Landmark Report Finds Major Flaws in the Cass Review

“These issues significantly undermine the validity of the Cass Review’s recommendations, such that the Review fails to fulfil its aims as commissioned and should not be used as the basis for policy.”

Archibald Tuttle // Wikimedia Commons

Almost two dozen researchers at a top medical journal have published a scathing scientific takedown of the Cass Review. Experts found that the NHS-issued report—a non-peer reviewed publication authored by Dr. Hillary Cass, a pediatrician without clinical or research experience with trans patients—was marred by “unexplained protocol deviations,” “methodological flaws,” and “unsubstantiated claims.”

Published on May 10 in BMC Medical Research Methodology, the report identified critical flaws in the study. The Cass Review led to a ban on puberty blockers targeting trans children in the UK. However, puberty blockers remain readily available to cisgender children, who may need them for conditions like precocious puberty.

“These issues significantly undermine the validity of the Cass Review’s recommendations, such that the Review fails to fulfil its aims as commissioned and should not be used as the basis for policy making,” the researchers said in a statement to Erin in the Morning.

The Cass Review has been rejected by countless medical organizations across the globe which oversee aspects of trans health care—including the World Professional Association for Transgender Health (WPATH), the Endocrine Society, The American Academy of Pediatrics, the Association of the Scientific Medical Societies in Germany, and the Royal Australian and New Zealand College of Psychiatrists, to name just a few.

Nonetheless, it continues to act as the vanguard for anti-trans lawmakers and leaders grasping at straws for a scientific basis to further an extremist political agenda. In addition to being the basis of the UK’s puberty blocker ban, conservative Supreme Court Justice Alito cited the Cass Review in oral arguments for United States v. Skrmetti, the ongoing court battle over the constitutionality of anti-trans health care laws in Tennessee. It also lends credence to anti-trans conversion therapy practices, which it repackages as “exploratory” therapy. The Review could be used as a pseudoscientific building block to wall off any and all sorts of trans-affirming care for children and adults down the line.

The BMC study reviewed seven different facets of the Cass Review, and found that all seven possessed “a high risk of bias due to methodological limitations and a failure to adequately address these limitations.” One major reason for such bias, in addition to the lack of peer review, is that the Cass Review failed to give actual trans people, their families, medical practitioners who specialize in trans care, or arguably anyone with expertise on the subject matter any real authority over the process.

“These flaws highlight a potential double standard present throughout the review and its subsequent recommendations, where evidence for gender-affirming care is held to a higher standard than the evidence used to support many of the report’s recommendations,” researchers wrote. “Considering this, and the Cass report’s poor understanding of transgender identities and experiences, it is vital to question the integrity and validity of the Review’s recommendations and the appropriateness of basing health policy on them. To uphold its commitment to evidence-based medicine, future gender-affirming care research must generate robust observational data, involve transgender communities, and prioritise patient-centred outcomes, ensuring validity, generalisability, and cultural relevance.”

The study reaffirms what many trans people, their families, and their doctors already know: Anti-trans extremists are using the veneer of science, medicine and concern to strip trans people of their autonomy and rights. But it’s not scientific, medical, or “cautious” to manipulate the data to bolster a radical, anti-trans agenda.