Americans have been believing in God less and less in recent months, and new research is shedding light on why that may be.

According to a survey conducted by the Pew Research Center as part of a broader Religious Landscape Study, 78 percent of people who do not identify with any religious group were raised in a faith system and then left as adults.

Further, about half of those people said that a lack of belief caused them to leave their faith, citing, among other things, "science" and "lack of evidence" as reasons for this skepticism.

"I'm doing a lot more learning, studying, and kind of making decisions myself rather than listening to someone else," one respondent explained in the survey.

About 20 percent of people who left their childhood faith oppose organized religion generally. "I think that more harm has been done in the name of religion than any other area," one respondent said. "I think religion is not a religion anymore. It's a business... it's all about money," said another.

Another 18 percent said they were religiously unsure, meaning that they had some connection to religion or spirituality but didn't identify with any particular religious group. One participant explained: "Right now I'm kind of leaning towards spirituality, but I'm not too sure. I know I can pray to my God anywhere. I do believe in a higher power, but I don't need a church to do that."