A new study claims that the internet is one of the main forces behind more and more Americans losing interest in religion.

Allen Downey, a computer scientist at the Olin College of Engineering in Massachusetts, published his paper "Religious Affiliation, Education and Internet Use" in the MIT Technology Review on Friday.

He uses data from the University of Chicago's General Social Survey to show that those with no religious preference numbered 10 per cent of the US population in 1990, but that jumped to 18 per cent in 2010. This amounts to approximately 25 million people.

Mr Downey also notes that the Protestant percentage of the US has dropped from 62 per cent in 1990 to 51 per cent in 2010. In 2010, over half (53 per cent) of the population spent at least two hours per week on line, and 25 per cent were online for more than seven hours.

At the same time, he points to how internet use has gone up from essentially zero per cent in 1990 to 80 per cent in 2010. He also notes that the percentage of university graduates in the US has increased in that same time from 17 per cent to 27 per cent.

Mr Downey examines the reason for this relative drop off in those identifying themselves as religious in response to the questions "what is your religious preference?" and "in what religion were you raised?"

He attributes an estimated 25 per cent of the decrease to an increasing lack of religious upbringing, 5 per cent to someone's level of education, and 20 per cent to the level of internet usage.

Speculating about why increased internet usage might cause declining religious observance, Mr Downey said: "For people living in homogeneous communities, the Internet provides opportunities to find information about people of other religions (and none), and to interact with them personally."

Mr Downey also argues that it is unlikely that the causal relationship is the other way around: "Conversely, it is harder (but not impossible) to imagine plausible reasons why disaffiliation might cause increased Internet use."

However he also notes that his work is about correlation rather than causation, saying: "This association does not prove causation; if A and B are associated, it is possible that A causes B, B causes A, or a third factor causes both."

Stephen O'Leary, an associate professor at the University of Southern California studying religion's presence on the internet, argues that the internet is just one part of a far broader sociological trend.

Speaking to the Religious News Service, Prof O'Leary said: "Let's call it the influence of the religious marketplace."

Prof O'Leary argues that as people have more choice, more people do not feel the need to make a specific choice or to be particularly observant.

"Internet use is part of that, but what it really does is magnify to a dramatic level the degree of choices one has," he says.

Other factors he cites are the Catholic Church's child sex abuse scandals: "That has, more than almost any other thing, alienated a whole generation. And it is not just Catholics. It goes to all religious authority by extension."

But Prof O'Leary suggests that just because people are becoming less affiliated with religion, that does not mean they are becoming atheists.

"They haven't given up their belief in the supernatural. They just don't feel they need organisations or institutions to bring it to them.

"You don't have to believe in any god to light a candle or hold hands and utter a mantra or chant."

Mr Downey also notes that his statistical model can only explain half the total religious decline: "So about half of the observed change remains unexplained."

While many would regard this as a call for criticism of the internet, university campus culture, or the lack of religious vitality in the home, Pastor Chuck Warnock sees Mr Downey's study as an opportunity.

Speaking on Ethics Daily, Pastor Warnock of Chatham Baptist Church in Chatham, Virginia, said: "Christians might be better served to investigate what in our contemporary way of life contributes to loss of faith for about 25 million of our fellow citizens."