First Outcome Study of the Dutch Protocol

In 2011, the Amsterdam research group led by child psychiatrist Annelou de Vries published the first study on the outcomes of the Dutch Protocol. Until then, only the approach had been described; see the 2006 publication.

What the study showed

The study followed seventy young people who received puberty blockers between 2000 and 2008. They were assessed before starting blockers and again shortly before starting sex hormones. During that period, depressive symptoms and behavioral problems decreased, while overall functioning improved.

What did not change

Gender dysphoria itself and dissatisfaction with their bodies did not decrease during treatment with blockers. All seventy young people subsequently went on to take sex hormones. This finding later became relevant to the debate over whether blockers really provide a pause for reflection.

The limitations

The group was strictly selected: it included only young people with dysphoria since early childhood, no serious mental health problems, and parental support. There was no control group, so it is not certain whether the improvement was caused by the blockers or by the support they received and growing older; the page on cohort studies in transgender healthcare discusses this type of research. In 2020, the UK NICE included the study in its assessment and rated the evidence as being of very low certainty; see the NICE review in the archive.

How the research was designed

Between 2000 and 2008, nearly two hundred young people were referred to the Amsterdam clinic. More than one hundred of them received puberty blockers. The study describes the first seventy who subsequently started sex hormones. At the first assessment, they were on average just over thirteen years old; at the second, almost seventeen. The young people and their parents completed questionnaires about low mood, anxiety, anger, and behavioral problems, while the researchers assessed overall functioning. Gender dysphoria and satisfaction with their bodies were also measured.

Differences between boys and girls

The outcomes were not the same for everyone. Among the young people assigned female at birth, dissatisfaction with their bodies increased rather than decreased during treatment with blockers. The researchers explained this by noting that blockers halt puberty but do not change the body in the desired direction: that only happens with hormones. Young people who dropped out or were not eligible were not followed in the study.

The British replication

The Tavistock gender clinic in London began its own study in 2011 to test the Dutch results. It followed 44 young people aged twelve to fifteen who received puberty blockers. The results were not published until 2021. Psychological functioning had neither improved nor worsened, and all but one of the young people went on to take sex hormones. The researchers concluded that the positive Dutch outcomes had not been replicated. This finding contributed to the later British reassessment; see the NICE assessments.

Significance

The study appeared at a time when the treatment was already spreading around the world: the international guideline recommending puberty blockers had been published two years earlier; see the Endocrine Society guideline. The recommendation therefore preceded the published evidence. This is not unusual in medicine when new treatments are introduced, but it explains why later assessments place so much weight on what this single group of seventy young people actually demonstrates.

The study provided the protocol with outcome-based support for the first time and was cited in guidelines. Three years later, a follow-up study examined the same group as young adults; see the 2014 follow-up study.