Why Do People Lead Secret Lives?

Those close to Paige Birgfeld knew her as a loving mother of three young children and an energetic small business woman. But police revealed this weekend that Birgfeld, who disappeared June 28, led another life, one kept secret from her friends and family: she ran a local escort service.

In doing so, the 34-year old Colorado resident appears to have joined the ranks of many seemingly ordinary Americans who lead hidden lives. News reports abound with stories of men with multiple families, married teachers who have illicit affairs with their students or otherwise upstanding businessmen who struggle with hidden drug problems or visit escort services.

The details of the Birgfeld case are still emerging and it's too soon to know what drove her to work in the escort business. Some forensic psychologists point to significant differences between runing an escort service and some other types of secret illicit activity, like having an affair with a student.

But forensic psychologists say that people who lead dual lives are often driven by many of the same factors, including easy money, personality disorders and the thrill of illicit and sometimes dangerous activities.

"There's no one profile," said Gregg McCrary, a retired criminal profiler with the FBI. "It's usually a combination of things -- money, emotional needs, the need to have a secret life, the need to be risk taking."

That duality can lead to dangerous consequences. "If the secret life is more rewarding than the normal life, then you may get addicted to the secret life," said forensic psychologist Katherine Ramsland. "The two lives are going to clash one way or the other."

Police Suspect Foul Play

Authorities now say that Birgfeld went by the name "Carrie" when dealing with customers of "Models, Inc.," an escort service that police say she ran.

Until Saturday, authorities in Colorado were treating Birgfeld as a missing person, even suggesting that she may have staged her own disappearance.

But new information about her escort agency, combined with a lack of any evidence indicating she voluntarily went missing, altered the investigative track over the weekend. Police are investigating potential clients who may have dealt with Birgfeld around the time she disappeared.

"We so far haven't found a single piece of evidence that indicated she left on her own free will," said Heather Gierhart, a spokeswoman for the Mesa County Sheriff's Office.

The Money Is Fantastic

Though it is still unclear what led Birgfeld to run Models, Inc., one possible -- and obvious -- explanation for behavior like Birgfeld's is money.

"Generally the primary motive is money," said ABC News Consultant Dr. Michael Welner, a forensic psychiatrist and the head of The Forensic Panel, adding that the escort business would allow someone in Birgfeld's position to quickly make a lot of money without any advanced education or training.

"Without interviewing her, my only frame of reference is what comes up time and again," he said. "And time and again the money is fantastic and you can't beat it."

Police say Birgfeld, the mother of three children, ages 8, 6, and 3, worked several jobs. In addition to the escort agency, she ran a chef's consulting business, taught dance to preschoolers and sold baby products.

The Grand Junction Sentinel reported that investigators have also visited a downtown office kept by Birgfeld, where they found a massage table and what appeared to be acupuncture equipment. Police would not confirm or deny the report

Joel Dvoskin, a forensic psychologist and the president of the American Psychology-Law Society, agreed with Welner's assesment.

"Logically, it's more likely that there's a financial cause," he said. "Very often, it's like Bill Clinton said: it's the economy stupid. Money is often why people do things."

A Reprieve From a 'Boring' Life?

Some people who have engaged in similar illicit behavior have been driven by psychological disorders and a desire to add excitement to their lives, experts said.

"More often than not, part of it is the thrill, adding excitement to an otherwise 'boring' life," said McCrary. "They want to have a dark secret, to walk on the wild side a little bit."

Working in the sex trade in particular can offer an allure of danger. "They acquire an aura of being sexy, which you don't necessarily retain after marriage and motherhood," said Ramsland.

Welner, though, disputed that characterization, saying that the sex workers he has treated are not attracted to the danger of the work.

What little is known about Birgfeld also appears consistent with some personality disorders, said Dr. Elliot Atkins, a forensic psychologist. Atkins suggested that working several different jobs while raising three children could be consistent with a need for approval and affirmation or with the manic activity associated with bipolar disorder.

People with bipolar disorder are often easily bored and are stimulated by stress of balancing different parts of their lives. They often engage in several projects at once and often engage in sexual indiscretions, he said.

"In this case, one of the things we wee is that she appears to be somebody who's very busy, engaged in multiple activities and multiple relationships," he said. "What we see is an individual who has an extremely high level of energy, or need for excitement."

All of Birgfeld's different activities are consistent with the "grandiose thinking of someone in a manic state," Atkins said.

Stress and Guilt

The stresses of leading a hidden life often leads people to unravel.

"Sometimes they react with volenece, sometime they will just slip away and start over somewhere," said Ramsland.

Usually able to separate the different facets of their lives, but may begin to take a toll through anxiety, depression and other mental illnesses, she said.

"If you have any conscience at all, you do begin to feel the guilt," she said.

Welner said that people who work in the sex industry often struggle to fit in to their communities. "Often they long for a day when they will have a legitimate life," he said.

It is still too early to tell which of the possible explanations best describes what happened to Birgfeld. Dvoskin also pointed out that there are differences between running an escort service and other notable types of hidden illicit activity, like having an affair with a student, that seem to be more a product of lack of impulse control.

"To run a business, that's not yielding to immediate temptation," he said. "That's a criminal enterprise."

But, until more is known, Birgfeld's friends and family will probably continue to be surprised by how little they actually know about the woman they thought they knew.

Martin Williams, a forensic psychologist, wondered, "You have to ask, is the escort service the exception or is the family life the exception?"

With Reporting By David Schoetz

ABC News Consultant Dr. Michael Welner is chairman of The Forensic Panel, a national forensic science practice. He is developing an evidence-based test called the Depravity Scale, http://depravityscale.org, which invites Americans to participate in surveys that are used to form a legal standard of what represents worst crimes.