The emotional well-being of parents is strongly linked to the successes and failures of their children – especially their least happy children-even after their children are grown up, according to a new study.

Researchers had assumed that having successful children would completely mitigate the effects of problem children. Surprisingly, however, they found that mothers and fathers were only as happy as their least happy child.

Lead researcher Professor Karen Fingerman from the University of Texas at Austin, said: “We had expected that a successful child might mitigate the negative impact of having a child who suffers problems. The successful child might give the parent something positive to focus on. But parents still seem to suffer even when one of their grown children does.

“It could be the case that parents empathise with their children’s distress, they are embarrassed that their relationships with these grown children suffer, or that grown children who have problems may place excessive demands on the parents,” she said. “Any one or all of these factors may contribute to parental worry and depression.”

The study is the first to look at the positive effects of having successful grown children and the aggregate effects of multiple children.

Most US parents have more than one child. This study was unique because it looked at how multiple grown children’s accomplishments and failures affect the parents’ psychological health.

Professor Fingerman and her colleagues collected data from interviews of 633 middle-aged adults regarding each of their grown children (1,251 total children). The study assessed the children’s problems, successes, the quality of parents’ relationships with each child, and the parents’ psychological well-being.

Having many children who were successful increased well-being for parents. However, when it came to children’s problems, it only took one child suffering one major life problem to drag down parents’ mental health, which manifested as depressive symptoms or increased worry. The more children who suffered problems, the more parents suffered.

Conversely, children who experienced successes in education, marriages and careers were more likely to maintain positive relationships with their parents. Relationship quality was directly tied to parental well-being.

Professor Fingerman speculates that parents are sensitive to positive and negative events in their children’s lives because it reflects on their own achievements in parenting.

“Parents have a distinct investment in grown children reflecting decades of child-rearing,” she said. The study was published last week in the Journals of Gerontology: Psychological Sciences.

Professor Fingerman’s co-authors include Yen-Pi Cheng of The University of Texas at Austin, Kira Birditt of the University of Michigan and Steven Zarit of Pennsylvania State University.