A new study from the University of Iowa finds that the limitations of human memory make it difficult for researchers to link adverse childhood experiences to physical health issues later in life.

The researchers found that so many people either forget what happened to them in childhood or don’t remember it clearly enough that asking adults about their experiences as children may introduce biases.

The study asked 454 African-Americans about adverse childhood experiences such as physical abuse, divorce, crime, and neighborhood violence. Researchers asked the respondents first when they were 10 years old and again when they were in their 30s.

The study found that respondents were less likely to report childhood traumatic experiences when they were 30 than when they were 10. For instance, 62% of the 10-year-olds reported being struck with a cord, belt, or other object as punishment. As 30-year-olds, only 33% reported that abuse. Similarly, 20% of 10-year-olds remembered being a victim of a crime or having a friend who was the victim of a crime. Only 8% remembered that as adults.

The respondents also reported illness symptoms that they suffered as adults and provided blood to calculate a biomarker of cardiovascular risk, so researchers could look for possible links between adversity in childhood and health risks as adults.

Researchers did find a link between adversities reported by the 10-year-olds and adult cardiovascular disease. However, beyond that, they found the childhood adversities only predicted adverse self-reported health if the adversities were reported during adulthood.

The authors conclude that the study offers further evidence that reports from adults may not be the best method to determine the association between childhood adversities and subjective health, and this method should be used with caution. Still, given the association between childhood adversities and cardiovascular health risk, adverse childhood experience should continue to be the target of policy programming including clinical intervention at the federal and local levels.

The study was part of the project, “Childhood Stressors and Cardiovascular Disease Risk in Adulthood: A Longitudinal Investigation of Divergent Explanatory Models,” supported by the University of Iowa Injury Prevention Research Center in the College of Public Health and funded by the U.S. Centers for Disease Control and Prevention (CDC). The research publication was co-authored by Mark Berg, associate professor in the Department of Sociology and Criminology and director of the Crime & Justice Policy Research Program at the Public Policy Center.