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Chew et al, 2018

Hormonal Treatment in Young People With Gender Dysphoria: A Systematic Review

Open Access


The authors review and summarise the medical literature on suppressing puberty with puberty blockers and cross-sex hormones in gender dysphoric young people. They focus their efforts on studies examining physical, psychosocial and cognitive effects.


The authors find 13 studies that met their inclusion criteria. Nine of these studies examined the effects of blockers. Of these, four examined physical effects, three psychosocial effects, and two cognitive effects.

The studies examining psychosocial and cognitive effects are listed below in Table 1. and summarised at the linked articles. We will update Fully Informed with a review of the studies examining the physical effects at a later date.

The authors assessed the studies risk of bias across three domains using a modified version of the Quality In Prognosis Studies (QUIPS) tool:

  1. Study participation (the study group represents the population of interest).
  2. Study attrition (whether some participants dropped out of the study and remaining participants reflect a potentially biased subsample).
  3. Outcome measures (researchers measured outcomes in a similar way for all participants).

The authors rated each study as having a Low, Medium, or High degree of bias in the three domains.

Table 1. Risk of bias and sample size
Vries et al., 2011¹Psychosocial70High BiasHigh BiasMedium Bias
Vries et al., 2014¹Psychosocial55High BiasHigh BiasMedium Bias
Costa et al., 2015²Psychosocial201Medium BiasMedium BiasMedium Bias
Staphorsius et al., 2014Cognitive116Medium BiasHigh BiasMedium Bias
Burke et al., 2014Cognitive62Medium BiasMedium BiasMedium Bias

The authors rated all of the psychosocial and cognitive studies as "Medium" or "High" degree of bias. Vries et al., 2014 has a high degree of bias in two of the three domains. Subsequently, the authors conclude that:

evidence regarding [hormonal treatments'] psychosocial and cognitive impact are generally lacking.

Compare this assessment to the wording in the New Zealand Guidelines used to report the evidence and describe the Vries et al. (2014) study (emphasis added).

There is good evidence that puberty blocking and gender affirming care for trans young people significantly improves mental health and wellbeing outcomes.


There are no high-quality studies on the cognitive and psychosocial outcomes of puberty suppression. Existing studies are few, small scale, with at least moderate degrees of bias. The paper on psychosocial outcomes with the least bias - Costa et al. (2015) - does not show significant outcomes between the treated and untreated groups.

When study authors use standardised evidence quality assessment tools, they report the evidence as weak and generally lacking³. When clinical practitioners make up the majority of a guideline author group - such as in the case of the New Zealand Guidelines - they can misrepresent the evidence (Lenzer et al., 2013).

Doctors prescribing puberty blockers must inform parents that the treatment is experimental and evidence of good outcomes is lacking.


¹ Vries et al., (2011) and Vries et al., (2014) studied the same group of participants.

² Chew et al. report a sample size of 201 for Costa et al. (2014). However, this was the initial group, and only 71 completed the full study period.

³ Heneghan and Jefferson also assess the evidence for puberty as having a high risk of bias.