PORTLAND — The number of women held in the Maine state prison system has grown nearly sixfold since 2002, a stark increase that experts say is sparking new conversations about the best way to rehabilitate female criminals.

Portland’s Holiday Inn By the Bay is the setting for the 2013 biennial Adult & Juvenile Female Offenders Conference, which attracted more than 400 corrections officials from multiple states for five days of specialized workshops and presentations.

Erica King, a University of Southern Maine policy analyst who has conducted extensive research into corrections systems and was a co-organizer of the conference, said Maine’s population of female prison inmates has grown from 25 in 2002 to 146 today.

And with each woman costing, by some estimates, nearly twice as much as a man to hold in prison, there’s a significant financial incentive to adopting programs and services geared toward keeping the women’s recidivism rate down, she said.

King said the reason for the explosive increase in Maine female prison inmates is hard to pin down. She said increased capacity for women, through the opening of the Department of Corrections’ Women’s Center in Windham in 2002, is sometimes pointed to as a catalyst. But she also said changes to sentencing guidelines at the state and federal levels in recent decades — for those convicted of drug crimes or being accessories to the crimes of others, for instance — have likely ensnared more women than in the past.

Whatever the legal drivers for the change, King and others who attended the conference on Tuesday said corrections officials must think differently about how they deal with incarcerated women compared to their male counterparts.

“Their pathways into the system are very different than men’s pathways into the system,” King said.

Piper Kerman, author of the bestselling memoir “Orange is the New Black” about her 13 months in a Connecticut prison, said a majority of women in prison have histories of trauma or being abused.

“A huge percentage of women in prison are in there for nonviolent offenses, and the vast majority of the women I was imprisoned with were not frightening at all,” Kerman, the conference’s keynote speaker, told the Bangor Daily News in a Tuesday interview. “Those women needed changes in their lives, but being a prisoner in a jail cell was not what got the best results.”

“Our mission as a justice system is to correct and restore, so (prisoners) leave our system better than they were before. And if we’re not addressing those histories of abuse and trauma, they’re more likely to go out and fall back into the lifestyles that got them into trouble in the first place,” said King.

Amanda Woolford, director of female services for the Maine Department of Corrections, said 78 of the women in state custody are in the longer-term Women’s Center in Windham, while another 68 are in the Reentry Center in Bangor, a less-restrictive environment for women with fewer than three years left on their terms.

Woolford said the system still needs “one more step” for women inmates beyond the Reentry Center, in the form of some kind of transitional housing to provide women safe places to live away from the abusive relationships that may have driven them to drug use or crime.

“Some women don’t have anywhere to go,” Woolford said. “We’re still dropping women off at shelters.”

Woolford said female inmates are much more likely to be incarcerated for crimes committed out of economic desperation or for “boyfriend crimes,” in which they’re pressured into serving as a getaway driver, prostitute or drug transporter for a controlling boyfriend or husband.

“The line between us and them is very, very thin,” she said. “I don’t know what I would do tomorrow if I lost my job and couldn’t feed my child, or if my husband was abusive.”

King said the cost to society of putting women behind bars is greater than it is for men in part because women are more likely to have children, who are in many cases moved into the foster care system when their mothers are incarcerated,.

She agreed with Kerman’s sentiment that more effective — and less expensive — punishments for women who committed nonviolent crimes could involve in-home monitoring or intensive counseling programs.

While no U.S. data on the subject was immediately available, a Canadian study found that women cost more than $113,000 per year to incarcerate, while their male counterparts cost just less than $60,000 annually. According to the Vera Institute of Justice, the average annual incarceration costs in the U.S., making no distinction by gender, is lower than in Canada.

The Vera Institute reported in 2012 that it costs Maine taxpayers about $46,000 per year on average to keep a person in prison.

King said Kerman’s book, which has since been adapted into a critically acclaimed television show by the same name, has “engaged a public that’s been a bit apathetic (about the subject of women’s needs in prison). And these are their tax dollars. How do they want them used?”