A troubled home life can literally make children sick - even after they become adults.
Researchers at the University of California at Los Angeles have found that children raised in "risky" families - high on anger and low on love - were more prone to develop mental and physical illnesses later in life.
The trend held up regardless of whether the families were rich or poor.
However, children who grow up in such homes aren't doomed to their fates, says study co-author Rena Repetti, an associate professor of psychology.
"There's a lot of hope," Repetti says. "All of these things can be changed. We're not saying the family environment sets chain reactions in motion that can't be reversed."
Repetti and her colleagues spent six years examining more than 500 studies that looked at how a family's "social environment influences [the children's] physical and mental health." Some of the studies followed groups of people for decades.
The researchers weren't surprised to find a link between a difficult childhood and mental illness in adolescence and later in life. However, they weren't expecting to see a definite connection with physical illness, Repetti says.
Children who grew up in "risky families" were more likely to suffer from diseases like cancer, heart disease, obesity, diabetes and hypertension. They were also more likely to die earlier, and have bouts with depression.
The researchers uncovered two major types of "risky" families. Some featured "high levels of aggression, overt conflict and expressions of anger," Repetti says, while the other type was "cold, unsupportive and neglectful."
Repetti and her colleagues speculate that children in "risky" families may not learn how to deal with stress properly.
"If you live in a chronically stressful environment early in life, you become hyper-responsive to stress later in life," she says. "There's a cumulative effect on the ability to respond to stress and recover from stress."
It's well known that stress can affect adults physically and mentally. Studies have shown that people under stress are more likely to get sick. Their wounds take longer to heal. They're more apt to be depressed, have high blood pressure and suffer heart attacks.
People who learn to control their stress, on the other hand, reap a host of health benefits. They have fewer headaches. Their memories are better. They may even be less likely to get cancer, studies suggest.
The children from risky families may also face extra challenges in dealing with people from outside their families, Repetti says. "They haven't had good role models at home in how to handle emotions," she explains.
Genetics might leave children open to physical and emotional problems later in life, too. They may inherit vulnerability to certain kinds of mental illness, and a stressful family environment may trigger that susceptibility, she says.
Obviously, not every child from a troubled home ends up mentally or physically ill as an adult. Repetti says that's because kids are exposed to many people other than their parents and siblings, and they encounter environments other than home.
Exposure and mentors
"Once they go to school and develop peer relationships, the exposure to other sources of influence increases exponentially," she says.
Joan Patterson, an associate professor of public health at the University of Minnesota, says often a mentor like a teacher or relative can make a major difference.
"There can be multiple places along the trajectory of one's life where supportive, caring, helpful people can enter and compensate for something that wasn't quite right in the family," she says.
Repetti emphasizes that people can also make changes later in life to offset the effects of their upbringing.
"People can learn how to cope with stress, how to regulate their emotional states, how to do things to reduce how they react to stress," she says.
The results of the research appear in a recent issue of the journal Psychological Bulletin.