By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Children who lose a parent suddenly may suffer a "double whammy" to their mental and physical health -- from the shock of the loss and because of inherited risks, researchers reported on Monday.

They said the risk factors that contribute to many early deaths of parents -- such as mental illness or alcoholism -- can be passed on to children. Such children may be more vulnerable to the stresses of losing a parent, the researchers said.

"Kids whose parents die early are at risk because the conditions that their parents have, that predispose their parents to early death, are also heritable and therefore they get both," said Dr. David Brent of the University of Pittsburgh School of Medicine.

Brent and colleagues studied 140 families in which one parent died prematurely and suddenly from suicide, accidental death, or sudden natural death.

The researchers, whose findings were reported in the Archives of Pediatric & Adolescent Medicine, were looking in particular for clues that the deceased parents may have passed a genetic or environmental tendency to their children, aged 7 to 25 at the time of the study.

"Parents who die suddenly are likely to have higher-than-expected rates of psychiatric disorder. Mood, alcohol and substance abuse, and personality disorders convey an increased mortality not only from suicide but also from accidents and cardiovascular diseases," they wrote.

They compared the bereaved families to 99 similar families with two living biological parents.

The children were assessed for psychiatric disorders, and their parents' psychiatric history was also checked.