Dutch Protocol research still lacks reliable evidence after 30 years, researchers conclude

The 'Dutch Protocol' — the treatment protocol developed in the early 1990s at the Amsterdam UMC Center for Gender Dysphoria — is internationally regarded as the starting point for medical transition in young people: first puberty blockers, followed later by cross-sex hormones. A new critical analysis, published in May 2026 in the European Journal of Developmental Psychology, reviews three decades of underlying research and reaches a stark conclusion: methodologically sound evidence for the effectiveness of this protocol is still lacking.

Three decades of in-house research, no independent evaluation

The authors, McDeavitt and Cohn, mapped all the research published by the Center for Gender Dysphoria itself over three decades. Their conclusion: however numerous the studies may be, none was based on a methodologically robust design. Large, prospective, controlled follow-up studies — the kind of research needed to establish cause and effect — are absent. Instead, the evidence base relies on small cohorts with limited follow-up and no control group. This assessment does not stand alone: independent systematic reviews and meta-analyses, including those by the UK's NICE in 2020 and the Cass Review in 2024, had already reached the same conclusion: the available evidence is 'remarkably weak'. An extensive dossier on that weak evidence base sets out the findings of all these evaluations side by side.

Who is evaluating their own work here?

A significant part of the analysis focuses on a narrative review published earlier in 2026, in which researchers from the Amsterdam center itself argued that their three decades of research do provide a sufficient basis for using puberty blockers and cross-sex hormones in adolescents. McDeavitt and Cohn point out that this review is not an independent evaluation: it was written by the same research group that produced most of the underlying literature. A field evaluating its own evidence base, the authors argue, is fundamentally different from an external, critical assessment — and precisely that external assessment has largely been lacking to date.

Known risks versus uncertain benefits

What the authors emphasize is the asymmetry between what is and is not established. The fact that puberty blockers and cross-sex hormones have physical effects — including permanent infertility and other medical risks — is relatively well documented. Whether these same treatments actually improve the long-term mental health of young people with gender dysphoria, by contrast, remains uncertain: the studies that should demonstrate this are precisely the studies the authors judge to be methodologically weak. This imbalance, they argue, should occupy a central place in discussions between clinicians, young people and parents about a treatment pathway they consider irreversible.

Why this extends beyond the Netherlands

The Dutch Protocol is not merely a Dutch matter. Clinics in the United States, the United Kingdom and many other countries adopted the protocol and its underlying assumptions over the past several decades as an international standard. A critical reassessment of the Dutch foundation therefore also affects the basis of gender-care guidelines far beyond the country's own borders. For policymakers and clinicians who invoke 'the Dutch approach' as evidence of a tried-and-tested, evidence-based method, McDeavitt and Cohn raise an uncomfortable question: what evidence exactly is that approach based on, and who has ever independently evaluated it? Stella O'Malley describes how the Dutch model falls apart under international scrutiny on genspect.nl.