The United Kingdom indefinitely extended a ban on puberty blockers for people younger than 18, barring medication prescriptions used to treat gender dysphoria, the government announced this week. There will be exemptions for people who choose to participate in a clinical trial aiming to study the safety and effectiveness of puberty suppression, which is set to begin next year. Young people already prescribed puberty blockers are allowed to continue taking them, the government said.

Britain’s health secretary, Wes Streeting, announced the decision Wednesday. He cited guidance from an independent panel that suggested prescribing puberty blockers to young people carries an “unacceptable risk” and recommended indefinite restrictions “while work is done to ensure the safety” of those treatments.

“Children’s healthcare must always be evidence-led,” Streeting said in a statement. “The independent expert Commission on Human Medicines found that the current prescribing and care pathway for gender dysphoria and incongruence presents an unacceptable safety risk for children and young people.”

The latest decision extends emergency measures put in place in the U.K. earlier this year to restrict the sale and supply of hormone medications that can suppress puberty, which may be prescribed as a form of gender-affirming care. In March, Britain’s National Health Service stopped routine prescriptions of puberty blocking drugs to children and teenagers under 18 at clinics, in response to a landmark review of the country’s approach to gender identity in health care. 

That review, conducted by a leading U.K. pediatrician, Dr. Hilary Cass, found insufficient evidence confirming puberty blockers were safe for young people. Cass reiterated that they “should only be prescribed following a multi-disciplinary assessment and within a research protocol.” She described the medications as “powerful drugs with unproven benefits and significant risks” in a statement responding to the health secretary’s announcement.

“I support the governments’s decision to continue restrictions on the dispensing of puberty blockers for gender dysphoria outside the NHS where these essential safeguards are not being provided,” Cass said. 

The government’s emergency ban took effect in May.

Streeting said new protocols for gender-affirming care will prioritize and implement targeted mental health services for transgender children and young people in the U.K., as well as their families.

“We are working with NHS England to open new gender identity services, so people can access holistic health and wellbeing support they need,” Streeting said. “We are setting up a clinical trial into the use of puberty blockers next year, to establish a clear evidence base for the use of this medicine.”

James Palmer, the medical director for specialized services at the NHS, said the agency welcomed the  government’s decision to extend the ban and also acknowledged its consequences for trans kids.

“This will be a difficult time for young people and their families who are affected, so we are extending an offer of targeted support to anyone affected by the banning order from their mental health services,” Palmer said in a statement.