Complaints by working mothers that they don't relax until they fall into bed at night have a physiological basis, Duke University Medical Center researchers report.
The researchers found that stress-hormone levels in working mothers rise when they wake up and remain high until bedtime. Increased levels of stress hormones may place these women at greater risk for health problems by weakening their immune systems.
The reason for the increased strain, researchers suggest, is the "second shift" common to working mothers -- that after leaving their paying jobs they go home and assume primary responsibility for child-rearing and household duties.
The researchers caution that their study, which was limited to women in clerical or customer-service jobs, may not hold true for those in managerial jobs who earn more money or have more control over their time.
Nor, they added, should their results be regarded as evidence that mothers should stay home. Studies have found that women with multiple roles -- workers, wife, mother -- have better mental health and may have fewer physical ailments than those who stay home with their children.