Researchers say losing a sibling when you’re a child can have a serious, long-term impact on your health.

Grieving for the loss of a loved one is a time often characterized by extreme stress.

In adults, the impact of grief on the body has been studied broadly, and has been linked to heart problems and other adverse health effects.

But much less is known about the impact of grief on children.

Now researchers at Aarhus University Hospital in Denmark have found that the death of a brother or sister in childhood is often associated with an increased risk of mortality in the short and long term for surviving siblings.

Published in Jama Pediatrics, the work is the first of its kind to focus on the effects of sibling death in childhood on bereaved siblings with a long-term follow-up time.

“It is estimated that nearly 8 percent of individuals could experience a sibling death in childhood, but much less is known about its health consequences,” Yongfu Yu, PhD, a research assistant at Aarhus University who led the study, told Healthline.

“Sibling relationships tend to be the longest and the most intimate in a family,” Yu added, “thus the death of a sibling can be a devastating life event, especially when this event happens at early ages.”

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Yu and his co-authors conducted a population-based study of more than 5 million children in Sweden and Denmark who survived the first six months of life.

Of that group 55,818 children (about 1 percent) experienced the death of a sibling in childhood.

In a 37-year follow up period, 537 of the individuals in the bereaved group died.

The researchers found that compared with the children who did not experience the death of a sibling, those in the bereaved group had a 71 percent increased risk of death from all causes.

Higher risks of death were in the first year following a sibling’s death, as well as in same-sex sibling pairs or siblings with a small age gap.

“Siblings of the same sex and close age tend to have more frequent interactions and experience greater feelings of warmth and closeness. At the same time, perceived conflict is expected to be great in siblings of the same sex or a close age, which might lead to the guilt of the surviving siblings about the death of their sibling,” Yu told Healthline.

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Dr. Thomas Buckley from the University of Sydney has written extensively on the physiological impact of bereavement.

He says Yu’s work fills a notable gap in the literature.

“This is an important finding, as the bulk of literature to date has focused on spouses and parents of the deceased,” he told Healthline.

“While death of a loved one is a natural phenomenon, and grief for most is a natural response,” he added, “bereavement can be one of the most stressful experiences humans encounter in their lifetime. Studies that quantify the risk of such stress are very important as they create an awareness of the associated risks among both the public and health professionals.”

Darcy Walker Krause is the executive director of The Center for Grieving Children. She says it is important that childhood grief isn’t overlooked or misinterpreted.

“Because society can be uncomfortable with grief, it is often pathologized or, with children, ignored, Krause told Healthline. “Children grieve, but they do grieve differently than adults. Young children, typically 6 and under, often do not understand the permanence of death. They ask many questions, sometimes extremely technical ones. And they fully grieve but often in quieter ways or in ways we don’t understand, such as acting out or exhibiting hyperactive behavior. The older they get, particularly in adolescent years, youth may withdraw and not talk and express their emotions,” she told Healthline.

Krause knows firsthand how grief can impact a young life. She lost her mother at the age of 15 and believes Yu’s research could explain her own mother’s struggle.

“My mother was a bereaved sibling. Her brother died when she was a young adult. They were very close and it haunted her her entire life. She died of a heart attack, and I wonder if this research sheds any light on that fact,” Krause said.

Yu says the underlying mechanism resulting in an increased risk of mortality is still unclear and more research is needed in this area.

“More death events could reflect genetic susceptibility, direct impacts on bereaved children by psychological stress through adverse patho-physiological pathways or behavioral changes, and indirect impacts through parents’ and other family members’ reactions such as behavioral changes,” he said.

Both Kraus and Buckley say it is essential those experiencing grief don’t neglect their own needs when mourning the loss of a loved one.

“One of the important things for people who are suffering a loss to do is to recognize that this stressful time represents a significantly increased risk to their own health,” Buckley told Healthline.

“For those who have existing health challenges,” Buckley added, “they should liaise with their usual healthcare professional and ensure they continue any current medications they may already be taking, as well as explore potential preventative therapies their healthcare professional might recommend. Additionally, they should seek out social support and not ignore any physical symptoms that they may experience during this time.”