A leading genital reconstructive surgeon said that the number of patients who regret their sex change surgery is rising.

Surgeon Miroslav Djordjevic, operating at a clinic in Belgrade, Serbia, said that the increase is especially rising in men who had surgery to look like a woman. Djordjevic said there were “crippling levels of depression,” suicidal thoughts and desire for reversals, reported The Christian Post.

“It can be a real disaster to hear these stories,” said Djordjevic. The surgeon said he performs approximately 100 surgeries per year, both in his Belgrade office and at Mount Sinai Hospital in New York.

“Definitely reversal surgery and regret in transgender persons is one of the very hot topics,” he said. “Generally, we have to support all research in this field.” Djordjevic revealed that all of the reversal surgeries he has performed have been on men over 30 who wish to restore their male genitalia. 

The surgeon also said that the average age of people undergoing sex-change surgery is lower and lower. He’s concerned that eventually it will be legal for minors to have sex surgery, but the surgery won’t be performed by him. “I’m afraid what will happen five to 10 years later with this person,” he said. “It is more than about surgery; it’s an issue of human rights. I could not accept them as a patient as I’d be afraid what would happen to their minds.” He also opposes the use of hormonal treatments for minors in preparation for sex-change surgery. “If you change general health with any drug, I’m not a supporter of that theory.”

Bath Spa University in the U.K. made a decision last week to block researchers from studying cases about sex-change surgery regrets. The university decided that the research is “politically incorrect,” and could expose the university to criticism.

Although psychotherapist James Caspian specializes in therapy for transgender people, he was refused permission to study sex-change regret cases. He said that Bath Spa University is violating “the most basic tenets of academic and intellectual freedom of enquiry.”