Not only was exposure to ACEs more common than expected, with more than 6 out of 10 patients reporting at least one ACE, many were exposed to multiple types of adversity. Most importantly, the more ACEs reported, the more likely the patients were to have serious physical health problems (cancer, heart disease, etc.), mental health problems (depression, anxiety, etc.), and engage in health-harming behaviors (smoking, alcohol abuse, etc.). Since this first study, these findings have been repeated in thousands of patients in the U.S. and around the world (Anda et al, 2006; Bellis et al., 2019).

Scientific evidence suggests that ACEs have such powerful effects on health and behavior because they cause stress-related reactions in the developing brain and body. These reactions can cause impairments in cognitive, social, and emotional development as well as in developing organ systems. The effects of chronic or cumulative or “toxic” stress emerge early and persist throughout the life cycle (Shonkoff, et al., 2012) and become “biologically embedded” (Miller, Chen and Parker, 2011), as the body physically attempts to adapt to this cumulative stress or “allostatic load” (McEwen, 1998).  Studies of both humans and animals indicate that the impact of early life adversity may even be transmitted across generations through epigenetic changes. Historical trauma can also play a role in increasing the likelihood that some communities, families, and individuals will experience more trauma and stress in childhood.