A major study of the health of transgender and gender-nonconforming young people in the United Kingdom will begin later this year.

The study will include up to 3,000 children and teens whose gender identity differs from the gender they were assigned at birth and have turned to the country’s National Health Service for treatment, The New York Times reports. Researchers will look at participants’ physical, mental, and social health.

It will be funded by the NHS and the U.K. government’s clinical research agency and will be conducted by King’s College London as part of a larger King’s College project to determine how the NHS can best serve this population.

“Participation in the study will be voluntary and it will be observational in nature, meaning researchers will not alter any treatments the children are receiving,” the Times notes. “The researchers will survey the individuals and their parents or caretakers over several years without providing additional interventions.”

The study comes at a time when gender-affirming care is under attack in the U.K. The nation last year banned the provision of puberty blockers for people under 18 except for participants in clinical trials after a review by pediatrician Hilary Cass, called for more research into gender-affirming care for trans youth. However, her review has been widely criticized.

For instance, medical groups from Germany, Austria, and Switzerland came together to release guidelines supporting this care. They contended the Cass Review is full of methodological flaws and misrepresentations. Trans rights groups added that it set a higher bar for evidence of the effectiveness of gender-affirming care than for other treatments.

After the review came out, the NHS closed the U.K.’s only clinic providing gender care for youth and opened several regional ones aimed at taking a holistic approach to gender dysphoria, with much emphasis on mental health. The study will look at the care provided by these centers.

Emily Simonoff, a professor of child and adolescent psychiatry at King’s College who will be the chief investigator of the study, told the Times it will help resolve questions about gender-affirming care. “What we hear from young people and their parents and caregivers is that they’re worried about the lack of robust evidence to guide what treatment is going to be most helpful for them,” she said, also noting that “a lack of evidence base allows toxic views to be more rampant.”

“What is clear from the current evidence as highlighted is there’s no single story or experience that defines these young people,” said Michael Absoud, who will be a lead investigator as well. “This study is about listening to them — understanding their stories and their journeys and building a robust evidence base that reflects that diversity,” he added.

However, there is much evidence for the effectiveness of gender-affirming care, and in the U.S., it is endorsed by every major medical association.

Some supporters of this care welcomed the study. “Investments in research and clinical trials should be lauded,” Scott Leibowitz, a U.S. child and adolescent psychiatrist who is on the board of the World Professional Association for Transgender Health, told the Times. But he worried about the effects of the puberty blocker ban on youth in the U.K.

King’s College is also planning a study of puberty blockers, in which participants would be able to receive the treatment despite the ban, but it is still awaiting approval by regulators.