Tanya and Mike Mulligan are now suing the adoption agency for damages, because they say they weren't told of their children's psychological conditions.
But in court records obtained by "20/20," the adoption agency argues the Mulligans agreed to assume the risk that their adopted children "could arrive with undiagnosed physical, emotional, mental and /or developmental problems."
The Mulligans' lawsuit is pending.
Eventually, after life became unbearable, the Mulligans sent their daughter to a boarding school specializing in behavioral issues. But after two years, they realized they could no longer afford the $40,000-per-year tuition. In June, Margarita returned to her home in Tampa.
"We are doing everything in our power not to return them," Mike Mulligan said. "We didn't set out to do this [adoption] to just, you know, simply exchange them or give them back."
"I didn't want perfect children," his wife said. "But I didn't want a child that was going to hurt me. I didn't want a child that was going to disrupt my family and disrupt my marriage and make my relatives turn against me. I didn't want children that would make us feel like outcasts in our own neighborhood, isolate us and make us feel humiliated."
In the last 20 years, foreign adoption has become more popular; Americans now adopt about 19,000 children per year from overseas. While the vast majority adjust successfully, surveys suggest anywhere from 10 percent to 25 percent of foreign adoptions end in disruption.
Disruption refers to the ending or "disrupting" of an adoption. The majority of these children are from eastern Europe and have spent their formulative years either in institutionalized state-run care or with family members ill-equipped to care for them.
In some cases, the biological mothers of these children suffer from alcoholism, leading children to suffer from fetal alcohol syndrome. Many of these children also have bonding and attachment issues.
Like the Mulligans, many adoptive families deplete their savings and cash in retirement funds to pay for the doctors, tutors, psychologists and therapists that their kids need.
The Department of Health and Human Services says that 81 children adopted from overseas were put into foster care in 14 states in 2006. For kids who are 16 and older, JobCorps -- which helps students learn a trade, earn a high school diploma or GED and get help finding a job -- is an option as a sort of aging-out program.
But an undocumented number of children are simply lost, part of an underground, undisclosed network of children who are transferred between families, adoption experts say.
At its most desperate, the situation between adoptive children and parents can turn deadly. Since the early 1990s, the murders of 15 Russian children by their adoptive parents have been documented.
"People don't understand. These kids come at you every day … many times a day," Tanya Mulligan said. "It's like a battering ram and they just keep at you and keep at you and keep at you. And finally, they'll do something that endangers either a pet, or you or another child in the family and you snap."
Peggy Hilt, 36, was one of those adoptive parents who snapped. She's serving 17 years in a maximum security prison in Virginia for the 2005 murder of her adopted daughter, Nina, 2.