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Children who are maltreated face more than twice the risk of developing heart problems in later life than those who enjoyed a happy childhood, a groundbreaking New Zealand study reveals.
It shows that stress caused by maltreatment up to the age of 10 shows up physically more than 20 years later.
The University of Otago research found that "maltreatment" could range from extremes such as sexual or physical abuse to relatively minor disruptions such as frequent changes of the primary caregiver, although it was often a combination.
Thirty-three per cent of those who suffered in some way as a child had at the age of 32 "clinically relevant inflammation levels" - swelling caused by stress, which acts as an early indicator of health problems including heart disease, diabetes and lung problems.
Of those who were not maltreated, only 18 per cent had the same levels.
Associate Professor Richie Poulton, the study's author, told the Herald it showed that health was "the cumulative experience of a lifetime".
"It's the first study in the world to show a strong biological, plausible link between stress at a young age and physical health outcomes in later life.
"It's been speculated about for thousands of years, but we have here the evidence."
The research was carried out by the Dunedin Multidisciplinary Health and Development Research Unit, which has been tracking 1000 children born in the early 1970s in one of the world's longest-running health studies.
Inflammation is the body's natural response to stress, but increased levels can become a health risk. Mildly elevated levels of the swelling can go undetected for years, but are associated with illness such as heart disease.
Professor Poulton said it was "a wake-up call for New Zealand and also for the rest of the world".
The findings were released yesterday in the American journal Proceedings of the National Academy of Sciences.
The study also showed that the link between maltreatment and inflammation was not caused by growing up in poorer families or with a less healthy lifestyle.
"This suggests that there is something about childhood maltreatment, presumably the experience of traumatic stress in a critical phase of development, which specifically influences inflammation processes across the lifespan," the study concluded.
Professor Boulton said links had long been drawn between poor treatment during childhood and psychiatric problems and criminal behaviour in later life. But this study provided the first evidence of a physical health link.
