"In higher doses, or if it's repeated, [it] is disruptive to nerve cell growth," said Anda. "The growth and connection between nerve cells can be disrupted in small or big ways."
Ultimately, he said, excess amounts of adrenaline and cortisol could affect how people felt years later, and other effects have been suspected.
"It appears as though it affects immune function," he said.
Other researchers affirmed those findings.
"Traumatic stress early in life can impair the development of sensitive physiological systems and neurological networks," said Carrion. "We know from our research that early life stress can alter hormonal systems and brain function."
At the same time, the psychological effects alone can signal a shortened lifespan after a negative childhood.
"The [effects] of traumatic experience usually involves severe disregulation of emotional functioning," said Felipe Amunategui, an assistant professor in the division of child and adolescent psychiatry at Case Western Reserve University in Cleveland, Ohio. "This alone is associated with interpersonal difficulties, academic underachievement, and a problematic pattern of substance use. All these factors alone are associated with a reduced life expectancy. Add them together and they conspire so seriously limit life expectancy."
While researchers attempted to limit confounding factors, it is unclear how much of the shortened lifespan of childhood trauma sufferers owes to the trauma and how much arises from other factors in childhood.
"When we think about childhood trauma, it is important to consider the sorts of environments that give rise to these kinds of difficult experiences," said Rahil Briggs, an assistant professor of pediatrics at Montefiore Medical Center in New York. "It is likely that there were a host of other risk factors present in those environments, such as neglect, exposure to second hand smoke, etc., all of which may have also affected the reduction in lifespan."
"Children who live in communities where they are exposed to [childhood traumas] may also experience other socioeconomic disadvantages, such as problems with nutrition, lack of early recognition by pediatricians and lack of environmental stimulation," said Carrion. "However these factors may be inherent in the definition of having a history of high [levels of childhood trauma]."
He noted that many most people in the CDC study were in a similar health care program, which may limit that variation.
Anda acknowledged these limitations on the study. "Probably people that have a lot of adverse childhood experiences have a lot of other events we didn't measure," he said.
At the same time, he said, childhood traumas can lead to poor life decisions, and so many of those other factors that would shorten lifespan arise because of the negative events in childhood. However, he said,
Unfortunately, Anda said, the ACES study does not have an intervention arm to see what can be done to limit the impact of a traumatic childhood.
But, he said, some things have been tried that result in a better outcome for children who would otherwise be affected by a bad home life. One example is a home visitation program by a nurse who works with the family to assess the risk of certain problems in the home. Such programs have seen a reduction in child abuse risk.