Stressed-out parents are not only damaging their own health - they may also be making their children more vulnerable to illness.
Research shows that stressed mothers and fathers have more sickly children than their more chilled-out friends and colleagues.
While it is well-known that stress can affect a person's own health, putting them at higher risk of heart attacks and other ills, it now seems a parent's mental state can have a knock-on effect on their children's physical health.
The researchers, from the University of Rochester in New York, asked the parents of almost 170 healthy children aged between five and 10 to monitor their child's health over three years.
Although fathers were free to take part, mothers were more likely to volunteer for the task.
The parents were asked to record symptoms of illnesses among their children each week and take their temperature when they were unwell.
Every six months, the adults took a test designed to assess their own psychiatric health, including symptoms of anxiety and depression.
More than 1,000 periods of illness were recorded in the youngsters during the study period, with the children more likely to be unwell in the winter.
However, analysis showed a disproportionate amount of ill-health, including fever, among youngsters whose parents were under stress.
The team also measured the levels of immune cells in the children and found those with highly-stressed parents were much more likely to have heightened immune activity - a sign they were working hard to fight off infection, this week's New Scientist reports.
This contrasts with stressed-out adults, who tend to have weakened immune systems.
The researchers concluded that more work was needed on the factors behind susceptibility to infection.
Dr David Jessop, a University of Bristol expert on stress and the immune system, described the study as 'fascinating' but cautioned that the results could have been skewed by stressed-out parents being more likely to believe their children to be ill when they weren't.
"Parents should not become overly concerned because the study is quite small and raises more questions than it answers," he said.
"The number of illnesses in children could be over-reported because the parents are more anxious. We need to know much more about how parental stress can have this effect on children's health."
Previous studies have shown stress in pregnancy raises the risk of premature birth. High levels of stress hormones in the womb many also have long-lasting effects on the brain of the developing child, with stressed-out mothers-to-be running double the risk of their toddlers having lower than average IQs.
The children are also more likely to be hyperactive, have emotional problems, not do as they are told and suffer from stress themselves.