The BMJ cover this https://www.bmj.com/content/385/bmj.q837
One emerging criticism of the Cass review is that it set the methodological bar too high for research to be included in its analysis and discarded too many studies on the basis of quality. In fact, the reality is different: studies in gender medicine fall woefully short in terms of methodological rigour; the methodological bar for gender medicine studies was set too low, generating research findings that are therefore hard to interpret. The methodological quality of research matters because a drug efficacy study in humans with an inappropriate or no control group is a potential breach of research ethics. Offering treatments without an adequate understanding of benefits and harms is unethical. All of this matters even more when the treatments are not trivial; puberty blockers and hormone therapies are major, life altering interventions. Yet this inconclusive and unacceptable evidence base was used to inform influential clinical guidelines, such as those of the World Professional Association for Transgender Health (WPATH), which themselves were cascaded into the development of subsequent guidelines internationally