Fewer than half of U.S. adults say shared faith is a very important indicator of a successful marriage, but religiously mixed households can create unexpected consequences for couples, as well as their future children, according to a new Pew Research Center report on religion and family life.

"Adults who were raised in interfaith households say religion was a less prominent feature in their lives when they were growing up, compared with those in religiously matched families," researchers noted.

Thirty percent of adults raised by parents with different faith backgrounds and 24 percent of those who had one religious parent and one who is not religious say religion was very important to them growing up, compared to 43 percent of those raised by a religiously matched mom and dad.

Pew's survey offers an overview of how the religious make-up of a household impacts family members at a time when more Americans are being raised by parents of different faiths. Nearly 1 in 3 millennials (27 percent) was raised in a religiously mixed home, compared to 19 percent of baby boomers and 20 percent of Generation X.

These new findings are based on an analysis of Pew's 2014 U.S. Religious Landscape Study, which surveyed more than 35,000 adults, and a recontact survey of 5,000 of the original respondents. The margin of error is 2.0 percentage points.

Here are three of the survey's key takeaways on religiously mixed households:

1. Interfaith marriages may weaken religious practice

Americans worry more about a couple's shared interests and sexual compatibility than their religious background when it comes to predicting the success of a marriage, Pew reported. But before getting serious with someone from a different faith background, people should consider how a religiously mixed relationship might affect their own spiritual habits.

Pew's study showed that people in interfaith marriages are less likely to say religion is important in their life, attend worship services regularly, pray frequently and believe in God — all markers of what Pew calls being "highly religious" — than their counterparts in religiously matched marriages.

More than 8 in 10 Protestants (82 percent) married to fellow Protestants are highly religious, compared to 58 percent of Protestants married to non-Protestant believers and 59 percent married to someone unaffiliated with a faith, or nones, Pew reported. There's also a large gap in religiosity between Catholics married to other Catholics (70 percent are highly religious) and Catholics married to nones (46 percent.)

These findings don't prove causation, researchers noted. In other words, someone in a mixed marriage who isn't highly religious may not have been religiously active when they were single.

But the findings give reason to believe that for a couple where one has stronger faith, that rarely rubs off on their less-religious counterpart.

"Being married to a religiously affiliated spouse seems to have little impact on the religiosity of religious nones. Just 13 percent of religious nones married to a religiously affiliated spouse are highly religious, which is only modestly higher than the 9 percent of nones married to fellow nones who are highly religious," Pew reported.

2. There may be fewer opportunities to discuss faith

Two-thirds of married adults (67 percent) say they discuss religion "a lot" or "some" with their spouse, Pew reported.

The frequency of these discussions falls when comparing religiously matched couples to religiously mixed ones, but around half of believers married to someone in a different denomination (62 percent) or someone who is religiously unaffiliated (46 percent) still regularly talk about faith.

Additionally, 3 in 10 people with a different faith background than their partner say religion often sparks arguments, Pew reported.

The findings showed that differences in belief do cause tension in some cases, which can affect a family's ability to thrive religiously.

Partners who practice different faiths may struggle to pray together, which relationship experts sometimes suggest couples do in times of conflict, the Deseret News reported earlier this year.

"When people pray (about tensions in their relationship) they are helped to see their part in the problem. They're helped to see what they can do themselves to make a difference. And they are helped to soften," noted Mark Butler, a professor of marriage and family therapy at Brigham Young University, in the article.

Couples who share an understanding of the role religion plays in their relationship may also be able to handle marital stress better, such as in the wake of an affair. "The couple may believe that God has a mission for their marriage, and perhaps even brought them together," the Deseret News reported in September.

Even a slightly lower frequency of religious discussions may have big consequences for a couple's children. Pew's study showed that a child's future religious practice depends, at least in part, on whether or not he or she felt their parents cared a lot about their faith.

For example, "among people with an exclusively Catholic background, for instance, three-quarters of those who say religion was very important to their family while they were growing up (73 percent) describe themselves as Catholics today, compared with just 38 percent among those who say religion was 'not too' or 'not at all' important to their families," Pew reported.

3. Religiously mixed households produce unaffiliated kids more often

In general, the new study showed that children raised in religiously mixed households are more likely than their peers in religiously matched homes to describe themselves as nones when they're adults.

One in 4 adults raised by one Protestant parent and one Catholic parent (26 percent) is religiously unaffiliated, compared to 19 percent of adults who were raised in an exclusively Catholic home and 14 percent of adults raised in an exclusively Protestant home, Pew reported.

Additionally, "nearly 4 in 10 (38 percent) of those who say they had one parent who identified with a religion and another parent who was religiously unaffiliated describe themselves as nones today," the study noted.

This disaffiliation from religion was likely driven by a variety of factors, one of which may be that interfaith couples are less likely to participle in religious activities with their kids.

For example, 77 percent of religiously matched parents pray or read scripture with their children, compared with 60 percent of partners who practice different faiths and 43 percent of couples with one member who is a none.

"Religiously affiliated parents married to spouses who share their faith … are also more likely than others to do volunteer work with their children, though the gaps between" them and other parents are more modest in this case, Pew reported.

Email: kdallas@deseretnews.com, Twitter: @kelsey_dallas