Dr. Susan Bradley, a Canadian psychiatrist and pioneer in child gender dysphoria treatment, came out against the popular model of affirming children’s transgender identities and putting them on puberty blockers — a practice she was once involved in — in an interview with the Daily Caller News Foundation.

Bradley started a pediatric gender clinic in 1975 aimed at treating children with gender dysphoria — a deep sense of discomfort with one’s body and biological sex — in which she offered a therapy-focused approach; most patients outgrew their feelings of being transgender over time, she told the DCNF. Around 2005, the clinic began prescribing puberty blockers to gender-dysphoric children as a way to alleviate their distress, a model which has since become widely adopted by medical establishments around the world, including in the U.S.

Bradley, who is now in her early eighties, expressed regret that the clinic had participated in the administration of puberty blockers for gender dysphoria, which she now believes can cement a child’s sense of confusion out of which they would likely otherwise grow. She also expressed concern about the drugs’ side effects.

“We were wrong,” she said. “They’re not as irreversible as we always thought, and they have longer term effects on kids’ growth and development, including making them sterile and quite a number of things affecting their bone growth.”

While most children who experienced gender dysphoria typically grew out of it and came to accept their bodies and gender prior to the widespread implementation of the “gender affirmation” approach, numerous doctors expressed concerns that puberty blockers made children’s temporary gender confusion permanent by solidifying their sense of actually being the opposite sex, according to The New York Times. The drugs also prevent the surge in bone density that would normally occur during puberty, with some patients experiencing lifelong bone issues. The FDA also identified six cases where there was a “plausible” link between GnRH agonists and a condition called pseudotumor cerebri, which is caused by elevated fluid pressure in the brain.

Bradley told the DCNF her opinions on puberty blockers evolved over time.

“We thought that it was relatively safe, and endocrinologists said they’re reversible, and that we didn’t have to worry about it. I had this skepticism in the back of my mind all the time that maybe we were actually colluding and not helping them. And I think that’s proven correct in that, once these kids get started at any age on puberty blockers, nearly all of them continue to want to go to cross sex hormones,” Bradley said.

Bradley opened the Clarke Institute of Toronto’s Child Youth and Family Gender Identity Clinic (GIC) in 1975, and she went on to become the head of Child Psychiatry at the Hospital for Sick Children and the psychiatrist-in-chief and head of the Division of Child Psychiatry at the University of Toronto.

“An opinion from someone like Dr. Bradley has enormous potential to influence debate because she is what Cass Sunstein has called a ‘surprising validator,’” Joseph Burgo, psychotherapist and vice director of Genspect, told the DCNF. “It’s human nature to dismiss even well-reasoned arguments and credible evidence from those who are readily identified as on the other side, as ‘them’ — say, Republicans, or well-known ‘transphobes.’ But Dr. Bradley is a pioneer in the field and politically unaligned.”