"People often say that children are resilient and they'll bounce back, but we found that there are events that can have long-term consequences on adult health," said Kenneth Ferraro, distinguished professor of sociology and director of Purdue's Center on Aging and the Life Course. "In this case, people who were frequently emotionally or physically abused by their parents were more likely to have cancer in adulthood, and the link was greater when mothers abused daughters and fathers abused. Overall, the more frequent and intense the child abuse, the more it increased the cancer risk.
"We would like to see child abuse noted as an environmental factor that can increase cancer occurrence in adulthood. More research on this topic also could help mediate the effects or improve interventions to help abused children."
The research, which was conducted with sociology and gerontology graduate student Patricia Morton.
"We started examining a variety of childhood misfortunes, including abuse, and when these were all combined, we found that men with the most stressors during childhood were more likely to develop cancer," Morton said. "Second, we found that when children were abused by their same-sex parent, it increased their cancer risk."
The researchers can't say exactly why that is, but a possible reason is the effect of the greater social bond between same-sex children and parents.
"Other studies have shown that if a mother smokes, the daughter is more likely to smoke, and the same relationship is found when sons mirror their father's behavior," Morton said. "More research is needed, but another possibility is that men may be more likely to physically abuse their sons, and mothers are more likely to physically abuse their daughters."
The study's findings were based on survey data from 2,101 adults in two waves of the National Survey of Midlife Development in the United States. Abuse was one of many childhood misfortunes - including loss of parent, poverty, poverty and family educational status - that researchers examined to determine if there was a link to cancer in adulthood.
In the first analysis, the research team found that men who experienced the most cumulative stressors during childhood were more likely to have cancer. This was not true with women, and this suggests that men and women may have different responses to childhood stressors, Morton said.
The second analysis looked at each category of misfortune, and this is where the connection between abuse and cancer was revealed. Survey participants were not directly asked if they were abused, but abuse was defined by survey answers to questions such as how frequently a parent, sibling or other person insulted or swore at them as a child; refused to talk them; threatened to hit them; pushed, grabbed or shoved; threw something at them; kicked, bit or hit them with a fist; choked them; or burned or scalded them. The frequency of these abuses also was identified. The link was still there when controlled for the adults' age, lifestyle choices and economic status, but the researchers would like to look closer at these mechanisms.
"It also is likely," Ferraro said, "that the effect between child abuse and cancer is underrepresented in our study, because people who suffered abuse and were then incarcerated, placed in a mental institution or died were not included in this survey of adults. These groups may represent people with more acute and severe effects from abuse, and even though they are omitted, we still find a link."
The researchers are now examining potential links between child abuse and other health outcomes, including heart attacks and types of cancer.
"The connection between negative childhood events and mental health is accepted, and these findings reinforce that such events can also have a long-lasting effect on a person's physical health," Morton said. "It's shocking just how much the damage sticks, and it is a reminder that childhood, which is defined by rapidly changing biological systems, is a sensitive period of development."