Anne Mannering of Oregon State University in Corvallis, Ore., and colleagues say theirs is the first study done on the link between marital issues and infant sleep that unambiguously eliminated the role of shared genes between parents and children.
The researchers interviewed more than 350 families with adopted infants to eliminate the possibility that shared genes influenced the relationship between marital instability and child sleep problems.
"Our findings suggest that the association between marital instability and children's subsequent sleep problems emerges earlier in development than has been demonstrated previously," Mannering said in a statement.
The study, published in the journal Child Development, found marital instability when children were nine months old predicted increases in sleep problems at 18 months -- even after factoring birth order, parents' anxiety and difficult infant temperament.
The researchers said they did not find the reverse to be true -- children's sleep problems did not predict marital instability.
Notable deaths of 2014 [PHOTOS]