FRIDAY, March 25 (HealthDay News) -- Even very young children can get stressed by depressed parents who display negative emotions toward them, researchers confirm.

The new study included 3-year-old children who were subjected to different harmless, but stress-inducing, situations, such as causing them to become slightly nervous or frustrated. After each stressful event, saliva samples were taken from the children to measure levels of the stress hormone cortisol.

The researchers also observed the interaction between children and their parents -- usually the mother -- as they did a task together or as the parent read a book to the child.

The largest stress responses were seen in children whose mothers had been depressed at some point in the child's life and whose mothers also displayed hostility -- frustration, anger, annoyance or critical comments -- when playing with their children.

There weren't enough fathers in the study to offer a sense of how they interact with children, and depression was less common among fathers, said Lea Dougherty, of the University of Maryland, and colleagues at Stony Brook University.

Stress is a risk factor for depression. These findings suggest one way that a parent's depression can lead to depression in a child, the study authors explained.

The report is slated for publication in an upcoming print issue of the journal Psychological Science.

The findings are "actually quite hopeful, because, if we focus on the parenting, we could really intervene early and help parents with chronic depression when they have kids," Dougherty said in a news release from the Association for Psychological Science.

More information

The Nemours Foundation has more about childhood stress.