It's no secret to students that coed dorms are more fun than same-sex dorms. But they can also fuel very unhealthy behavior that might otherwise be moderated.

A new study finds university students in coed housing are 2.5 times more likely to binge drink every week. And no surprise, they're also likely to have more sexual partners, the study found. Also, pornography use was higher among students in coed dorms.

Some 90 percent of U.S. college dorms are now coed.

More than 500 students from five college campuses around the country participated in the study. Among the results:

42 percent of students in coed housing reported binge drinking on a weekly basis.

18 percent of students in gender-specific housing reported binge drinking weekly.

While that doesn't put coed housing on par with fraternity and sorority houses, the researchers note that binge drinking isn't exclusively a "Greek problem."

"In a time when college administrators and counselors pay a lot of attention to alcohol-related problems on their campuses, this is a call to more fully examine the influence of housing environment on student behavior," said Jason Carroll, a study coauthor and professor of family life at Brigham Young University. BYU was not one of the participating campuses.

The findings are detailed in the Journal of American College Health.

A separate study in 2007 found that college exacerbates the innate predisposition of some young adults to become heavy alcohol users. In effect, going to college can fuel alcoholism.

In light of the finding, the natural question is whether a selection effect is in play. For example, do partiers and teetotalers sort themselves out in the housing application process?

That doesn't appear to be the case, the researchers said in a statement today. College housing offices generally assume students prefer coed housing and give them the option to "opt out" if single-gender housing is available. Very few exercise that option.

"Most of the students who live in gender-specific housing did not request to be there; they were placed there by the university," said Brian Willoughby, lead author of the study. Willoughby recently earned a Ph.D. from the University of Minnesota and returned to BYU as a visiting professor.

A wealth of information on the study participants allowed the researchers to examine other factors that could predict binge drinking. Their statistical analysis took into account the effects of age, gender, religiosity, personality and relationship status.

"When we first identified these differences with binge drinking, we felt certain that they would be explained by selection effects," Willoughby said. "But as we examined the data further we found that the differences remained."

The participating campuses included two public universities in the Midwest and another on the West Coast, as well as a liberal arts college and a religious university on the East Coast.