A surgeon friend told James Caspian that in one year he’d performed two reverse gender reassignment operations on patients who’d swapped gender then changed their minds. “This is new,” he said. “Someone should research it.” Caspian, a psychotherapist at a private gender clinic, discovered no one ever had. So he enrolled on an MA course at Bath Spa University with the intention of writing his thesis on “detransition”.

No one could accuse Caspian, a slight, thoughtful gay man, of being hostile to trans people. He is a trustee of the Beaumont Trust, a gender educational charity, and in 16 years as a counsellor had hundreds of patients who, after working through childhood and emotional problems, concluded that “changing their gender presentation makes them more free to be themselves”.

There was another reason Caspian wanted to research detransition. A few years ago his patient profile changed from mainly adult men to younger women, many with complex mental health problems including social anxiety, self-harm, depression and undiagnosed autism. Some had been sexually abused as children. Many were lesbians, often fearful of coming out. But they saw changing gender as a panacea.

He’d read accounts by US women who, after having mastectomies and taking testosterone, had reverted to living as female. He feared that as the number of women patients increased so would regrets. “But I want to stress I didn’t know the answer: I just wanted to find out.”

He outlined his detransition thesis but was told by Bath Spa it must go before the ethics committee, which last November issued an extraordinary judgment. “Engaging in a potentially ‘politically incorrect’ piece of research carries a risk to the university,” it said. “Attacks on social media may not be confined to the researcher but may involve the university.” The report expressed concern that Caspian would suffer psychological damage. “It’s ridiculous,” he said. “I’m in my late fifties, I’m an expert in my field and I’m not even on social media. I’m not frightened at all.” Nonetheless his thesis was rejected.

So why is detransition a “politically incorrect” subject, likely to attract online attacks? Because, says Caspian, it concerns the issue of “gatekeeping” by medical professionals. In previous eras, trans people endured cruel, undignified battles before doctors permitted them treatment. Campaigners have succeeded in making this process simpler and more humane. But lately trans activists have argued that any requirement for psychological counselling is insulting. The mere fact they “self-identify” as the opposite gender is proof enough.

Detransition therefore is heresy. It suggests some “gatekeeping” is required: that it is misguided to allow ever younger people to take sterility-inducing hormones and have life-altering surgery without professional constraints. Detransition undermines the whole push towards instant, early diagnosis demanded by groups such as Mermaids and administered by Helen Webberley, the Welsh GP interviewed this week in The Times, who is under investigation for giving cross-sex hormones to 12-year-olds.

“We have to ask questions,” says Caspian. But trans activists label all academic inquiry as transphobic. An event organised by the London think tank Opus entitled “Attacks on Thinking in the Age of LGBTQWIIAP+” was, ironically, cancelled this week after an online petition and threats of disruption. Since I’ve been writing about this subject, I’ve been contacted by doctors, psychotherapists and concerned transgender people themselves, desperate to speak out on the trans phenomenon but terrified to do so for fear of abuse or even losing their jobs.

Caspian, who has left the field of gender counselling, is prepared to be the whistleblower. “We are seeing,” he says, “what Jung called a ‘collective complex’.” He compares this mass hysteria about being trapped in the wrong body to the “glass delusion”, an odd medieval phenomenon where people believed they were made of glass and might shatter. Other clinicians mention the 1990s faux scandals of satanic ritual abuse and false memory syndrome. But unlike them, gender anxiety is supercharged by the internet.

That is not to say any experts I’ve met dispute the existence of gender dysphoria or the need for better treatment and social tolerance of trans people. But they feel what they call the “trans trend” needs analysing as a cultural phenomenon as much as a medical one. “St Paul’s School suddenly has a lot of non-binary girls,” said one child gender expert, “but when I was growing up, that’s where all the anorexics went.”

There is no blood test or pathogen to diagnose you as trans; it is solely a matter of interpreting human experience. With children, the dominant interpretation that is currently shouting down all others is that, say, a boy who enjoys “female” toys or clothes must really be a girl.

And now trans activists are pushing for the American treatment strategy called “affirmation”, where doctors cannot challenge a patient who declares they are trans. Trans activists are lobbying hard to change an NHS policy document called the “memorandum of understanding”: they want to extend a ban on gay “conversion therapy” to include gender identity. In other words, a counsellor could no longer suggest that a patient’s belief they are in the “wrong body” is, for example, anxiety about being a lesbian or a reaction to sexual abuse. They would be silenced or risk malpractice suits.

James Caspian expects to receive abuse and threats. But he’s had enough of ignoring a phenomenon that is growing exponentially, may damage many lives, yet is barred from public debate and academic inquiry. “Asking questions,” he says, “is not a hate crime.”