Mary said she grew up believing that marriage was forever.

But when her husband went off to find himself, he discovered a network of friends who supported any choice that brought personal happiness. And Mary, who asked that her real name not be used, eventually found herself divorced.

Shakespeare wrote of love as a fever. Divorce, it appears, also can be catching.

Research by three academics — Rose McDermott at Brown University, James Fowler at the University of California at San Diego, and Nicholas Christakis at Harvard University — indicates that divorce can be contagious, spreading between friends, siblings and co-workers.

Even the divorce of a friend's friend can influence a person's decision to divorce.

The researchers recently published a paper with the catchy title, "Breaking Up Is Hard to Do, Unless Everyone Else Is Doing It, Too."

The research paper examined the effects of divorce within social networks (the real-life kind, not the Internet variety). It was based on data from a long-term study involving more than 12,000 people.

The researchers wrote that "men and women appear to be equally susceptible to splitting up if their friends do it." They noted that children reduce a parent's "susceptibility to being influenced by peers who get divorced."

Divorce tends to occur in clusters within social networks, the researchers found.

According to their research, a person with a divorced sibling is 22 percent more likely to get a divorce. A person with a divorced co-worker is 55 percent more likely to get a divorce. And a person who has a divorced friend is 1 1/2 times more likely to get divorced.

And distance doesn't diminish a person's influence: A divorced friend or family member who lives hundreds of miles away may have as much sway as a person who lives next door, the researchers asserted.

"The contagion of divorce can spread through a social network like a rumor, affecting friends up to two degrees removed," they wrote.

Last month, the news broke that former Vice President Al Gore and his wife, Tipper, were separating after four decades of marriage. Soon after, it was revealed that the Gores' eldest daughter, Karenna Gore Schiff, also was separating from her husband. Karenna's sister, Kristin Gore, divorced her husband last year.

In Mary's case, no one in her family ever had been divorced. But when her first husband went through "that seeking time in his life ... he found validation for his feelings" from his new circle of friends, and so he set into motion the chain of events that eventually led to divorce, she said.

At the time of her divorce, Mary, of Lancaster County, was attending a conservative Christian church in which it seemed almost no one was divorced. Needing spiritual solace, she kept quiet about the breakup of her marriage.

When she needed to share her feelings, she turned to her best friend, who also happened to be divorced. "She would say, 'Yes, it's OK that you're so angry that you cannot speak,'" Mary said. "She really knew, on a very deep level, what I was going through."

Divorce wasn't something Mary ever had expected to experience. But having a close friend who had been through it and survived it, helped her to survive, too, she said.

Mary said she sees how a couple's marriage can be influenced by the people around them.

Professionals who work with divorced couples can see this influence, too. They said they were not surprised by the research on divorce as a contagion.

"It made sense to me," said Kim Rosenberg, a Manheim Township psychologist who offers couples therapy and individual counseling. "It's not counterintuitive by any stretch of the imagination."

"We are influenced by what other people are doing. In the culture we live in, that makes sense," she said. "We are, first and foremost, social beings. We start in relationship, we stay in relationship. ... Our survival way back when — and still — is dependent on other people."

Nicholas V. Martino Jr., a psychologist with Life Management Associates in Lancaster County, agreed that "people in a group tend to reinforce each other's behavior, and act more similarly."

He said that when a person dies, his death affects his entire social network, in small and large ways. "It's the same thing with a divorce — it's going to affect the whole network," he said.

Sharon Blantz is the care and support pastor at the Worship Center, a nondenominational church in Upper Leacock Township. Blantz, who is divorced, said that "anybody who's been divorced would encourage people not to do that — they know the pain that's involved."

Sandy Atkins, who's also been through a divorce, now leads a biblical divorce recovery program called DivorceCare at the Worship Center with her second husband, Mike. She described divorce as "devastating."

"It's not fun," Atkins said. "Yeah, you're single again, but you face all kinds of issues that you didn't face when you didn't have any responsibilities."

She said she cannot envision many divorced people "happily saying to their friends, 'Oh, you have to get a divorce, because it's so much fun out there.' "

But often, Martino said, people don't even realize they're being influenced. No one is going to say, " 'So-and-so got a divorce, so it would be OK for me to get a divorce,'" he said. "It's more of an unconscious decision process."

Rosenberg said that when people see others in their social network getting divorced, they may feel reassured that divorce is something they can risk. They may feel that " 'I'm not risking this social group, and that social group. I won't be shunned,' " she said.

Being the first person in a family or social group to be divorced may feel akin to being a canary in a coal mine. "People don't like being the first in their family to be divorced, because there is that lingering stigma," Rosenberg said.

Alan Booth is a distinguished professor of sociology, human development and demography at Penn State University, who has done extensive research on divorce. The authors of "Breaking Up" cited his research in their paper.

He said he believes divorce can be contagious, but he thinks "it's only contagious among people who mean something to you."

"The people we're close to are sort of like us," Booth said. "We pick out our friends, and associate with co-workers, who have similar values to our own. People just tend to be attracted to people like themselves."

So if someone you like and respect gets a divorce, your viewpoint may expand to include the possibility of divorce, even if you hadn't considered it an alternative before, he said. "It's hard to get a divorce when people don't approve of it."

If you're a confidante to a friend whose marriage is in trouble, Booth said, you may reevaluate your own marriage, leading you to "see your spouse in a different way." And if that friend chooses divorce, you may experience it vicariously, seeing what effect it has on your friend, he said.

Martino, the psychologist, said he's heard people express concern about a spouse talking to a friend who's experiencing marital problems, or who has gone through a divorce.

"The spouse I'm talking to is concerned about the influence that these other people may have on their spouse," he said.

According to "Breaking Up," there is some reason to be concerned.

This does not mean that people should cut themselves off from friends who are experiencing marital difficulties, said Bill Melone, the care ministries pastor at LCBC, a church in Manheim.

"You can't be socially isolated," he said. "You don't want to cut yourself off from friends who have been divorced ... but you should purposefully look for people who can help [your marriage] in a positive way."

There was a time when churches were reluctant to provide divorce ministries because they worried that such programs would be viewed as an endorsement of divorce. Now, the program DivorceCare is offered not only at the Worship Center, but at LCBC and other churches across Lancaster County.

"Divorce is out there anyway. ... We accept that it happens, but that doesn't mean we're saying it's a good thing," Melone said.

Approximately 50 percent of American marriages will end in divorce within the first 15 years, according to the U.S. Census Bureau. And as "Breaking Up" notes, remarriage tends to be "even less successful than first marriage."

"When people heal, we don't want them to make the same mistakes," Melone said. "If their second marriage is going to happen, we want them to learn from their first failure."

According to the authors of "Breaking Up," there is a flip side to the contagious nature of divorce: Strong marriages may be contagious, too.

They suggest that "attending to the health of one's friends' marriages serves to support and enhance the durability of one's own relationship."

To Melone, this is an affirmation of one LCBC program, in which married couples who have weathered marital strife serve as mentors to other couples facing similar crises.

Psychologist Rosenberg also appreciated the conclusion of "Breaking Up." She said it was "such a positive, heartening take on all of this," that "we need to support one another's marriages, and support the health of those marriages."

Mary, who was divorced after nearly two decades of marriage, now is happily remarried to a man whose first marriage also ended in divorce. Grateful to have found each other, they have been helping another married couple work through difficulty. "We just want to love them and pray them through this," Mary said.

What worries Mary is research that suggests that children whose parents are divorced may be more prone to seeing their own marriages fail. "I really pray that this is not the case for my kids," she said.

She added: "I think my kids are going to be very intentional about being highly invested in their relationships."