Infants exposed to their parents' marital discord may be more likely to experience sleep issues during toddlerhood.
That's the conclusion to a new study published in the journal Child Development. Specifically, the study found that marital instability when an infant was 9 months old predicted whether the child would have issues falling asleep and staying asleep at 18 months of age.
"It's important to be aware of how the quality of the marital relationship might influence a child's functioning," says Anne M. Mannering, Ph.D., the lead author of the study and an instructor at Oregon State University. "It may be important earlier in [a child's] development than people may think."
Mannering and her team followed 357 families, all of whom had adopted infants during the first three months of the child's life. None of the infants followed in the study were genetically related to their parents or had any major medical conditions.
"We only looked at adoptive families ... to rule out the possibility that any relationship that we see between sleep issues and marital problems are due to shared genes," explains Mannering.
Each family's parents were interviewed when their infant was 9 months old. To measure what, if any, degree of marital instability each couple was experiencing at the time, they were asked "fairly serious" questions about their union, including whether either partner had considered divorce or separation. The parents then independently answered a questionnaire about their child's ability to fall asleep and stay asleep during the night.
Mannering and her team then conducted follow-up interviews when each child was a year and a half. Both parents were asked to answer the same questions from their first interview about their marriage and their child's sleeping patterns.
"We found that marital instability when infants are 9 months of age can predict sleep issues when at 18 months of age but we didn't find the opposite," says Mannering. So a child's sleep difficulties didn't predict the parents' marital disharmony.
"Sleep patterns did not predict marital instability later on," she said.
While Mannering's study does not explain what biological mechanism is behind the association between marital strife and sleeping patterns, she hypothesizes that stress in the child's environment could play a role.
"There's previous evidence that young infants' experiences can definitely shape brain systems that respond to stress very early on," says Mannering.
CNN Wire 2011