ANN ARBOR (AP) – University of Michigan researchers will interview 3,000 American adults as part of an $8 million study of how religion and health are related, the school announced Tuesday.

The John Templeton Foundation is financing the study, which seeks to establish “solid explanations for why religion has both positive and negative effects on human physiology,” the Ann Arbor school said in a statement.

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Public health professor Neal Krause and four colleagues from other schools will conduct the study.

Small sample sizes and other research method problems have plagued much of the research on the subject conducted so far, Krause said.

“Research has shown, for example, that people who go to church more often have better health. But we don’t know if this means that religion makes people healthier or whether only healthy people are able to get to church in the first place,” Krause said. “In order to unravel this and a host of similar issues, you have to follow the same people over time.”

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Krause said there is strong evidence religion “can be associated with better health” but said the picture is complex.

“It is more accurate to say that religion appears to improve the health of some but not all people. In fact, there is some evidence that there may be harmful aspects of religious involvement for some individuals,” he said. “The only way to unify a field is to develop a deliberate plan to do so. So far this has not happened in the religion and health field.”

Other researchers on the project are Robert Emmons of the University of California-Davis, Peter Hill of Biola University, Gail Ironson of the University of Miami and Kenneth Pargament of Bowling Green State University.

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