A study of hundreds of adult HIV patients found that a quarter of them were sexually abused as children.

The findings surprised Duke University researchers, who examined the health of 600 people between the ages of 20 and 71 who are infected with HIV.

More than half of those studied had experienced physical or sexual abuse during their lifetime.

Half of them had experienced three or more significant traumas in their lifetime, such as witnessing domestic violence, losing a child or witnessing a parent's suicide.

What's more, those who'd been through psychological traumas such as these were more likely to be in poorer health. They missed doses of medication, had unprotected sex and visited the emergency room more often.

"For whatever outcome we looked at, psychological trauma ended up being a predictor of worse medical outcomes and poorer health-related behaviours," lead author Brian Pence said.

But the reasons aren't clear. The researchers expected to attribute the counterproductive behaviour to post-traumatic stress disorder, depression or other mental health problems suffered by many with a history of exposure to trauma. But they found that even those without mental health issues had poorer health outcomes.

Pence said the study shows the importance of taking into account a patient's "trauma history."

"Regardless of the reason," he said, "past trauma certainly seems to influence how HIV patients engage in their medical care and how they end up doing clinically."

The findings appear in the Journal of Acquired Immune Deficiency Syndromes.