This content was created by the National Sleep Foundation

A new study of more than 350 families found that marital instability when infants are 9 months predicted difficulties falling asleep and staying asleep when they were 18 months old. This finding held true even after considering factors like children’s temperaments, parents’ anxiety levels, and birth order. However, the researchers found that the inverse wasn’t true—children’s sleep problems did not predict marital instability.

Researchers studied adoptive families contemplating divorce, thus ruling out genetic factors and focusing only on how family stress may affect a child’s development.

“Our findings suggest that the effects of marital instability on children’s sleep problems emerge earlier in development than has been demonstrated previously,” according to Anne M. Mannering, who was a research associate at the Oregon Social Learning Center when she worked on the study; she is currently with Oregon State University. “Parents should be aware that marital stress may affect the well-being of their children even in the first year or two of life.”