A 'mother's work is never done,' according to the old saying, and researchers found that the mental toll of the round the clock responsibilities of being a mum wears women down.

The findings suggest that women who feel overly responsible for household management and parenting are less satisfied with their lives and partnerships.

Researchers say tasks - such as knowing who needs to be where, on what day and at what time, and buying bigger clothes before a child outgrows their current clothes - require mental and emotional effort.

They said such tasks are examples of the 'invisible labour' women contribute while caring for their families.

Researchers from Arizona State University (ASU) and Oklahoma State University examined how invisible labour impacted on the well-being of a sample of American women.

Senior author Professor Suniya Luthar, of ASU, said: "Until recently, no one stopped to think about mum herself.

"We need to attend to the well-being of mums if we want children to do well, and also for their own sakes."

Though men participate in housework and childcare more today than in the past, the research team said women still manage the household - even when they are employed.

Because the unequal burden can affect the mental health of women, the researchers decided to study how the management of a household was divided among partners and how the division of labour affected women's well-being.

First author Dr Lucia Ciciolla, Assistant Professor of psychology at Oklahoma State University, said: "Even though women may be physically doing fewer loads of laundry, they continue to hold the responsibility for making sure the detergent does not run out, all the dirty clothes make it into the wash and that there are always clean towels available.

"Women are beginning to recognise they still hold the mental burden of the household even if others share in the physical work, and that this mental burden can take a toll."

The researchers surveyed 393 women with children under age 18 who were married or in a committed partnership.

A large percentage of the women also felt that it was mostly them who were responsible for monitoring their children's well-being and emotional states.

Almost eight in 10 said they were the one who knew the children's school teachers, and two-thirds indicated it was them who were attentive to the children's emotional needs.

But instilling values in children was a shared responsibility.

Financial decisions were also listed as shared responsibilities, with just over half of the women saying they made decisions about investments, holidays, major home improvements and buying a car together with their partner.

Because previous studies have found participating in financial decisions to be empowering, the researchers predicted it would be positively associated with women's well-being.

But it was unexpectedly associated with low partner satisfaction, which the research team attributed to the addition of the task on top of the already high demands of managing the household and ensuring the kids' well-being.

The study was published in the journal Sex Roles.