It's not clear that these types of problems in the household actually cause kids to fail to reach developmental milestones as quickly as other children, and it's possible that there's no direct connection.
Still, the researchers said the findings point to the importance of screening children for signs that they're exposed to violence or parental stress, because social workers could then try to help them stay on track in terms of development.
"Likewise, children that fail to attain important developmental milestones should be screened for intimate-partner violence and parental psychological distress so that these risk factors may also be addressed if present," said Amy Lewis Gilbert, an assistant professor of paediatrics at the Indiana University School of Medicine and the lead author of the study, which was published in the December issue of the journal Paediatrics.
Domestic violence involving couples in relationships affects an estimated 1.5 million women and 835 000 men in the United States each year, according to the study.
The numbers actually may be much higher, however, because some cases aren't reported. A 2011 study that reviewed existing research suggested that domestic violence affects 10 million children each year.
"We know unequivocally that family violence and parents' psychological stress affect children across the age spectrum," said Susan Campbell, a psychology professor at the University of Pittsburgh who is familiar with the study's findings.
Affected children have a tougher time psychologically, don't get along as well with other kids and do worse at school, she said.
It's difficult to figure out exactly how these and other factors affect kids, Campbell said, but they can be harmed by harsh and negative parenting, a lack of parental warmth and lack of support for learning.
In the new study, researchers looked at nearly 17 000 children under the age of 6 who were treated at four paediatric clinics in Indianapolis from 2004 to 2013. The parents of the children took surveys, and the study included an analysis of their answers.
Milestones of development
Almost half the kids were black, and 82% were on Medicaid or another public insurance. Parents of 2.5% of the kids reported domestic violence, and 12% showed signs of depression, anxiety or both.
Overall, more than one-third of the children hadn't reached at least one of several milestones of development.
The researchers, who adjusted their statistics to account for gender and ethnicity, found that kids whose parents were stressed or had experienced domestic violence or both were more likely than others to have problems with language, social skills and movement skills.
Campbell said the study has several weaknesses, however. It may have missed cases of domestic violence, depression and anxiety in parents, she said, and the findings don't account for the possible effects of two major factors: how much education the parents had and the number of parents who remain in the family.
"This is not a great study, but the message is important," she said. "If primary-care paediatricians and nurse practitioners are convinced of the lethal effects of family risk on children's development, maybe they will be more likely to provide referrals for intervention."
"Of course, this is a whole other topic, as there are not nearly enough quality services available for children living in families requiring a range of social services, even though decades of research underscores their effectiveness," she said.
For more about child development, try the US National Library of Medicine.
(Picture: Stressed parents from Shutterstock)