Children who lose their fathers early in life may be more likely to see a decrease in adult life expectancy, a new research has shown.

Presented Sunday at the 55th Annual Meeting of the European Society for Paediatric Endocrinology, the study looked at French children born between 1914 and 1916 — whose fathers were killed or injured severely during World War 1 — to understand the long-term effects of psychological stress on them.

Negative early life experiences, referred to as early life adversities (ELAs), have been linked to a person’s susceptibility to certain diseases as an adult. Even though effects of exposure to famine early in life — as in the case of the Dutch famine of 1944 or the Chinese famine of 1959 — have been studied using natural experiments, it has been tough to study the long-term consequences of psychological ELAs in natural experiments, because of a lack of historical data.

For the study its authors say is the first of its kind, the team of French researchers identified over 4,000 children matching the criteria — considered to have suffered ELAs due to an early loss of their fathers. They further determined whether the death had occurred while the child was in the womb, or after birth. A “control” of the same sex, age of mother, date and district of birth was chosen for each subject.

It was found that those with ELAs lost an average of one year in adult life expectancy, as compared to the controls. Children who lost their fathers while they were still in their mother’s womb saw a decrease in life expectancy by 2.2 years.

“The next step in the study will be to determine the cause of death for those having suffered ELA. This will shed light on the mechanisms involved,” Nicolas Todd, lead researcher of the team from Hôpital du Kremlin-Bicêtre, France, said in a press release.

“We know that deregulation of the stress response is commonly found on animal models of ELAs, so it will be interesting to see if any evidence of this can be seen in the causes of death in the French cohort. It may give us further insight into the long-term effects of ELA,” he added