People · Profile · Last reviewed 2026-07-13

Peggy Cohen-Kettenis

Clinical psychologist (b. 1948). First author of the 1998 case report on puberty suppression, co-author of the 2006 protocol description, and clinical psychologist at the VUmc gender clinic in Amsterdam. Widely regarded as the principal architect of the adolescent treatment model that became known internationally as the Dutch Protocol.

This profile summarises Cohen-Kettenis's role in developing and disseminating the Dutch Protocol, her main publications, and her influence on international guidelines. It also sets out the criticism her work has attracted in the subsequent debate. Contested claims are attributed to their sources; see Sources and further reading.

Role and career

Cohen-Kettenis trained as a clinical psychologist. According to the Cass Review she founded the Utrecht gender clinic; the 1998 case report was written while she was at the Utrecht university hospital, and she later worked at the VUmc gender clinic in Amsterdam. She became the central clinical-scientific figure behind the model of early medical intervention (source).

That model — puberty suppression from an early Tanner stage, followed by cross-sex hormones and, later, surgery — was first described for a single case in 1998 and set out as a treatment protocol in 2006 together with paediatric endocrinologist Henriette Delemarre-van de Waal. Cohen-Kettenis later worked at the VUmc gender clinic in Amsterdam until her retirement.

Key publications

Cohen-Kettenis & van Goozen (1998) — first published case of puberty suppression followed by cross-sex hormones in an adolescent.
Delemarre-van de Waal & Cohen-Kettenis (2006) — the description that established the treatment protocol.
de Vries et al. (2011) and de Vries et al. (2014) — the central follow-up studies that underpinned the protocol's international reputation.

The Utrecht Gender Dysphoria Scale

Cohen-Kettenis is associated with the Utrecht Gender Dysphoria Scale (UGDS), a self-report questionnaire that became a standard measure in Dutch gender research and beyond. Hermes Postma (Genspect) argues that this short self-report scale came to stand in for a fuller differential-diagnostic assessment; this is Postma's characterisation (see sources). See the glossary for a definition.

International influence

Beyond her clinical work, Cohen-Kettenis co-authored influential international guidance. She contributed to the WPATH Standards of Care and to the Endocrine Society clinical practice guidelines (2009, revised 2017), and served on the DSM-5 sub-workgroup that reclassified “Gender Identity Disorder” as “Gender Dysphoria”. Through these channels the Dutch model of early intervention spread to clinics worldwide — see Spread of the Dutch Protocol.

Criticism and debate

Cohen-Kettenis's work is now at the centre of an international reappraisal. Systematic reviews — including the Cass Review (2024), Sweden's SBU (2022) and Finland's COHERE (2020) — judged the evidence base for paediatric transition, much of it built on the Dutch studies, to be weak. See methodological criticism and sample size and attrition.

In a July 2026 essay, journalist Hermes Postma (Genspect) characterises Cohen-Kettenis as “the Dutch architect of a global medical scandal”. Postma argues, among other things, that follow-up cohorts suffered high attrition, that concerning mortality data in early cohorts received little emphasis, that the UGDS displaced proper differential diagnosis, and that a large majority of the treated adolescents in the 2011 cohort were same-sex attracted — raising the question of whether the protocol medicalised what would otherwise have been homosexual development. These are Postma's characterisations; the underlying studies and independent evaluations are documented in the studies and evaluations sections of this dossier.

A separate strand concerns governance: critics note that the same authors both produced the primary studies and co-wrote the international guidelines that cited them. In June 2026 the US FTC and four states sued WPATH over allegedly deceptive claims about paediatric medical transition.

Sources and further reading

Hermes Postma, “Peggy Cohen-Kettenis: The Dutch Architect of a Global Medical Scandal”, Genspect / Inspecting Gender, July 2026 — genspect.substack.com.
Origins — VUmc Amsterdam, 1980s–1990s and the three treatment phases.
Studies — overview and Evaluations — overview.
Timeline — chronological context, 1972–present.