The percentage of Americans who pray or believe in God reached a record low during 2014, according to new research published last week.

Led by San Diego State University psychology professor, Jean M Lange, the research team analysed data from almost 60,000 respondents to the national General Social Survey spanning the period between 1972 and 2014. They found that five times as many Americans said they never prayed in 2014 compared with responses of those in the late 1980s while nearly twice as many - 22 per cent - said they had serious doubts or didn't believe in God.

The study, the results of which were published in the journal Sage Open, also showed that Americans in recent years were also less likely to engage in a wide range of religious practices, including attending religious services, describing oneself as a religious person and believing the Bible is divinely inspired. The biggest declines were seen in the 18 to 29-year-old age group.

Dr Twenge, author of the book Generation Me, said that while previous studies had concluded fewer Americans were publicly identifying with a religion but remained just as religious in private ways, that was no longer the case.

"The large declines in religious practice among young adults are also further evidence that millennials are the least religious generation in memory, and possibly in American history," she said.

The one exception to the decline in religious beliefs was a slight increase in a belief in the afterlife. While in the 1970s only about seven per cent of Americans said they believed in life after death despite never attending religious services, in 2014 this figure had grown to 15 per cent (and as high as 21 per cent among young people).

"It might be part of a growing entitlement mentality - thinking you can get something for nothing," said Dr Twenge.