And the effect can last for up to 25 years, the research shows.

The researchers looked at a random 5% sample of UK death registrations among parents whose child had survived beyond the first year of life and those whose child had died before reaching a first birthday for the period 1971 to 2006. They included parents whose children had been stillborn.

The results showed that parents in Scotland were more than twice as likely to die or become widowed in the first 15 years after the loss of a child in the first year as those who had not been bereaved in this way.

Bereaved mothers were especially prone to an early death, the figures showed.

Bereaved mothers in England and Wales were more than four times as likely to die in the first 15 years after losing a child. And although the effects lessened gradually over time, they were still 1.5 times more likely to die than mothers who had not lost their child early, up to 25 years after the death.

It is commonly believed that people who lose their spouse/partner often die earlier than expected, commonly referred to as "dying of a broken heart," say the authors. Now it seems that this applies just as much to losing a child in infancy, they add.

They point out that they did not have sufficient data to rule out suicide, but suggest that the stress of a bereavement may leave a biological legacy, such as dampening down the immune system.

"Bereaved parents may also be more likely to use maladaptive coping strategies, such as alcohol misuse," which may in turn boost the likelihood of alcohol related illnesses or unintentional injuries, they say. Alternatively, stillbirth and infant deaths could be more common among parents who themselves have poor health, they suggest.

"It is imperative that cause of death be further investigated in order to establish the factors leading to increased mortality in bereaved parents," they conclude.