I know that many readers consider religion to be a delusion, an irrational obeisance to an "imaginary friend". Now it appears that research is being carried out at Utah State University into a condition where religious faith really does depart from the realms of normal sanity.

The condition, known as "scrupulosity", is a form of obsessive compulsive disorder that leads those afflicted to be "overly concerned that something they did might be a sin or other violation of religious or moral doctrine", according to the International OCD Foundation.

At Utah State, an assistant psychology professor, Michael Twohig, and a doctoral student, John Dehlin, are conducting ten-week studies of scrupulosity sufferers such as "Eric", a Mormon who became obsessed with confessing sins, even those he had not committed.

"Confessing sins that he actually did was not enough," the local Herald Journal reported. "He now had to start confessing sins he thought he did. 'I became convinced that I actually did those sins,' Eric said. 'If I had thought I had raped somebody, I would go confess that I had raped somebody. If I thought I had sex with a dog . . . I'd become totally convinced . . . and . . . I had to confess to my mission president again and again. In order to go heaven I was willing to do anything – even if it meant going to prison.' "

Dehlin told the Salt Lake Tribune that "if a person is prone to OCD and raised in a strict, orthodox home with religious teachings that include high stakes – on earth as well as the hereafter – he or she may be susceptible. 'You can't blame the parents, the person, the church, the religion,' he says. But, he adds, 'You don't hear about scrupulosity among Unitarian Universalists,' a faith that offers believers wide latitude."

It doesn't sound as though this condition is likely to affect too many Anglicans, then, either. What about those who belong to more demanding faiths, such as Catholics, Jews and Muslims? I referred last August to the philosopher Daniel Dennett's book Breaking the Spell: Religion as a Natural Phenomenon, in which he wrote about the appeal that "higher-tension", more "expensive" religious groups exerted. Previously I'd always thought of that as being one of their strengths. But rereading the relevant sentences made me pause:

An expensive religion is one that is high in "material, social and psychic costs of belonging". It doesn't just cost time spent on religious duties and money in the collection plate; belonging can incur a loss of social standing and actually exacerbate – not ameliorate – one's anxiety and suffering. But you get what you pay for; unlike the heathen, you get saved for eternity.

High in "psychic costs" was a bit I'd slightly skated over – but scrupulosity gives added weight to Dennett's words. I don't think, however, that the condition counts as a downside only of religion. Presumably somebody brought up in a household that followed a rigidly green moral code could suffer similar anxiety – or even one where any expression of sympathy for religion was equally frowned on. That search for certainty (over-certainty) is surely the cause of the problem. And aren't atheists just as prone to that as believers?