Most mothers who rely on children for care have a preference for which child they turn to in a crisis, confide in or prefer as caregiver, US researchers say.

Research by Megan Gilligan, a Purdue University doctoral student, and Jill Suitor, a professor of sociology, found older mothers were more likely to be stressed when they received help from an adult child not their preferred caregiver.

"When mothers received care from the adult child who was not their first choice, they reported more depressive symptoms, such as sadness, loneliness and sleep disturbances," Suitor said in a statement.

"Although mothers appreciated and acknowledged efforts from caregivers who were not their first choices, these children were less likely to share the mothers' values and to have the personal characteristics important to the mothers in selecting preferred caregivers. This incompatibility can have some strong negative effects."

Receiving care from a mother's preferred child did not affect the mom's psychological well-being, the researchers said.

"We expected having that preferred child care for a parent would make a positive difference, but surprisingly it didn't," Suitor said. "And we also found that mothers' depressive symptoms were higher when they received care from the non-preferred child than when they received no care from their offspring."

The study, published online in The Gerontologist, found being cared for by a non-preferred child was stressful because the alternate caregivers did not possess the social and emotional characteristics mothers expected.