The adverse childhood experiences study was a study conducted on approximately 17,000 adults aged an average of 57 years old, that examined the relationship between 10 categories of adverse and traumatic experiences in the first 18 years of life and physical health, mental health and social functioning outcomes. While it was common for people to have a score in at least one category of adverse childhood experience (ACE), two thirds reported scores in two or more categories, and one in six respondents had scores in four or more categories.

The study revealed that adults with high ACE scores were more likely to engage in behaviours that placed their health at risk, including alcohol and drug abuse, having multiple sex partners, cigarette smoking, and compulsive eating leading to obesity. Behaviours such as these are often negative coping mechanisms employed by the adult to deal with experiences such as emotional pain, anxiety, anger, and depression related to unresolved adverse childhood experiences. Adults with scores of 6 or more had a decreased life expectancy of approximately 20 years compared with those with lower scores, and a score of 7 or more was associated with a significantly higher risk of suicide.

The study also highlighted increased risk of disease amongst those that had high scores but did not engage in health-risk-taking behaviours. These participants were found to be more susceptible to stress related illness, as long-term exposure to chronic stress has been suggested to overstimulate the brain and body, weaken the immune system, and increase the risk of developing cancer and autoimmune disease.