In September 2009, 7-year-old Artyom Savelyev left Russia to live with his new adoptive family in Tennessee. Earlier this month, Artyom returned to Moscow — alone. All he had with him was a backpack and a note penned by Torry Hansen, a 33-year-old nurse and Artyom's adoptive mother.

"I no longer wish to parent this child," read the note, in part. The mother also reportedly said Artyom was mentally unstable.

The case has raised international furor, with Russian authorities suspending adoptions to the United States. It has also drawn attention to a rare but dark side of adoption: What happens when the bond between adoptive parents and children doesn't form.

Building a bond

Even for biological parents, bonding is complex. The hormone oxytocin, which induces maternal behavior in animals, helps to facilitate the attachment between mother and child.

But hormones are only part of the story. Attachments take time, and postpartum depression or other mental health problems can disrupt the process.

Bonding with adoptive children is similar. Some parents feel an immediate emotional connection, while others struggle for months or years. A study last month in the Western Journal of Nursing Research found that adoptive parents can experience "post-adoption depression" when their expectations about the adoption experience aren't met. These parents often report difficulty bonding with the child.

Disrupted adoptions

While bonding may be slow, most adoptions work out. According to a review of American adoptions in the book Clinical and Practice Issues in Adoption (Greenwood Publishing Group, 1998), 80 percent of placements make it to legalization. After the paperwork is in, the success rate was 98 percent.

But in extreme cases, the adoption "disrupts," and the child is sent back to the agency or foster home. This process is rarely as dramatic as Artyom's unaccompanied flight from Washington, D.C., to Moscow, but the case matches previous research in other ways. The risk of adoption disruption increases with age, from less than 1 percent in infants to up to 26 percent for kids adopted after age 15, according two 1988 studies.

The second of those studies, published in the journal Social Work, found a disruption rate of 10 percent for children adopted between the ages of 6 and 8. Artyom was 7 when he came to America.

Orphanage drawbacks

Artyom's childhood in a Russian orphanage may also have put him at risk. Research on children in Romanian orphanages found that kids with any institutional rearing had a 53 percent chance of psychiatric disorders compared with 22 percent for kids raised in a home. The study, published in 2009 in the American Journal of Psychiatry, also found that children randomly assigned to move out of an orphanage into foster care had rates of anxiety and depression half those of children who stayed in the orphanage.

When it comes to getting kids out of institutions, "the younger the better," said Charles Zeanah, a child and adolescent psychiatrist at Tulane University and author of the 2009 research article. "The less exposure to the institutional environment, the better chance that the kid is going to look better down the road."

Institutions often feature overburdened caregivers who work in shifts, Zeanah said. These caregivers can't bond with every child, and the children don't spend enough time with them to form attachments. Overcoming the effects of that environment can take years of hard work.

"Kids develop what we call survival behaviors," said Victor Groza, a professor of parent-child studies at Case Western Reserve University in Ohio. Aggression and violence can help kids survive in bad environments, Groza said, and kids "do not let go of those behaviors automatically."

Making adoptions work

Artyom's adoptive grandmother told the Associated Press that the boy exhibited many of these behaviors, including violent tantrums and attempts to set fires. But the boy was never evaluated by a mental health professional. Multiple studies in the 1980s and 1990s found that behavioral problems were a risk factor for disrupted adoptions, as was the parents' lack of flexibility in dealing with the behavior.

The key to successful adoptions is parental expectation, Groza said. Agencies must be sure that parents really understand the child's needs, and they must follow up with families who are struggling. Parents must understand that their child may need help, and they must be willing to delay gratification and reach out for support, Groza added.

"The likelihood is, things are not going to be bad, but you have to make sure that you have a plan and have gone through, 'What if this comes up, what if that comes up?'" he said.

It's a familiar strategy to Don Harris of Gilford, N.H., who adopted his daughters Molly and Hanna as babies from China. Hanna, now 10, turned out to have speech development problems and other special needs, likely as a result of sensory and nutritional deficiencies in the first 20 months of her life.

People have often asked "in a tactful sort of way," whether he would have adopted Hanna if he'd known how much help she'd need, Harris said. His answer is always the same: "Of course." He felt a bond within 24 hours of meeting Hanna, and the little girl — with her love of seashells, the color brown and hot-and-sour soup — has brought more joy into his life than he could have imagined.

"When you decide that you're going to adopt a child, it's a journey of faith," Harris said. "You need to understand why you're doing it, and you have to have a tremendous amount of faith that the referral that ends up in your hands was meant to be there."