Data from a recent study supports previous findings that specific neurobiochemical changes are linked to exposure to violence and abuse, several biological pathways can possibly lead to the development of illness, and certain physiological mechanisms can moderate how severe illnesses become in patients with past experience with violence or abuse. Recent studies give evidence of a link between stress occurring early in life and epigenetic modifications that last into adulthood. Adverse Childhood Experiences Study
The Adverse Childhood Experiences Study is a long-running investigation into the relationship between childhood adversity, including various forms of abuse and neglect, and health problems in later life. The initial phase of the study was conducted in San Diego, California from 1995 to 1997. The World Health Organization summarizes the study as: "childhood maltreatment and household dysfunction contribute to the development – decades later – of the chronic diseases that are the most common causes of death and disability in the United States... A strong relationship was seen between the number of adverse experiences (including physical and sexual abuse in childhood) and self-reports of cigarette smoking, obesity, physical inactivity, alcoholism, drug abuse, depression, attempted suicide, sexual promiscuity and sexually transmitted diseases in later life. "A long-term study of adults retrospectively reporting adverse childhood experiences including verbal, physical and sexual abuse, as well as other forms of childhood trauma found 25.9% of adults reported verbal abuse as children, 14.8% reported physical abuse, and 12.2% reported sexual abuse.
In the United States, interviews with parents reveal that as many as two thirds of documented instances of physical abuse begin as acts of corporal punishment meant to correct a childs behavior, while a large-scale Canadian study found that three quarters of substantiated cases of physical abuse of children have occurred within the context of physical punishment. Other studies have shown that children and infants who are spanked by parents are several times more likely to be severely assaulted by their parents or suffer an injury requiring medical attention. Studies indicate that such abusive treatment often involves parents attributing conflict to their childs willfulness or rejection, as well as "coercive family dynamics and conditioned emotional responses". Factors involved in the escalation of ordinary physical punishment by parents into confirmed child abuse may be the punishing parents inability to control their anger or judge their own strength, and the parent being unaware of the childs physical vulnerabilities.Children resulting from unintended pregnancies are more likely to be abused or neglected. In addition, unintended pregnancies are more likely than intended pregnancies to be associated with abusive relationships, and there is an increased risk of physical violence during pregnancy. They also result in poorer maternal mental health, and lower mother-child relationship quality.There is some limited evidence that children with moderate or severe disabilities are more likely to be victims of abuse than non-disabled children.