View Full-text Download PDF (1271kb)

The Cass Review (2024) was commissioned by NHS England as an independent review of the medical treatments offered to children with gender-related distress. It concluded that the clinical care for children questioning their gender identity was ‘remarkably weak’. The responses to the Cass Review provide a case study in what happens when a recommended course correction in medicine comes up against strong professional and institutional investment in an existing model of care. Reactions to the Cass Review went well beyond routine professional disagreements about clinical evidence. This paper examines some of the responses to the Cass Review through the lens of recent advances in our understanding of cognitive bias and defensive reasoning. Analyses of the responses reveal how evidence can be filtered through prior belief, group allegiance and efforts to preserve a coherent account of past and present judgement. The paper draws practical lessons from this episode. Cognitive biases are, by their very nature, unconscious but can leave tell-tale traces of their presence in observable behaviours. These can include rapid dismissal of unwelcome findings, disproportionate emotional reactions to disconfirming evidence and those presenting it, asymmetric scrutiny of evidence, shifting rationales to maintain a fixed course of action, and the tendency to treat some evidence as contaminated due to the source while accepting belief-consistent evidence more readily. Measures to minimise the influence of cognitive bias in clinical practice are proposed, including the systematic examination of disconfirming cases and rigorous red team exercises to challenge settled positions. These measures will not work unless they are embedded in a clinical culture where changing one’s mind is treated as a strength and a core feature of evidence-based medicine.

Keywords: Cass Review; gender dysphoria; gender-affirming care; cognitive bias; evidence-based practice