How Stressed Parents Affect Their Kids
A．When it comes to finding culprits for everything that’s wrong with us as children and even as s, parents are everyone’s favorite default option. And why not’ Decades of research in child development and psychology have linked depression from mother to children’s mental and physical illness as well as language defects, shown that when the parents’ marriage is broken by conflict, children grow up to be emotionally insecure and have difficulty forming loving relationships, and found that when parents are under significant stress, their kids are more likely to have behavior problems, to have difficulty handling stress, and to be at greater risk for mental illness. If there was any doubt about the power of this parental legacy, a latest study should prove it: when parents are under emotional, financial, or other forms of stress, it can alter their children’s patterns of genetic activity at least through their youth and perhaps longer. This is the first time scientists have ever found a link between parental stress in early childhood and the condition of their children’s DNA. As such, it represents the next frontier in the study of nature and nurture; identifying how the experiences we have (nurture) affect our DNA (nature). The groundwork was laid with research on lab rats, where scientists at McGill University showed that when mother rats devotedly lick and train their offsprings (动物幼子), it sets off a wave of changes: it activates a gene that makes a receptor for stress hormones (荷尔蒙) in the baby rats’ brains, which causes more receptors to be produced, fewer stress hormones to course through the rats, and the rats to be well-adjusted, curious, and mature rather than stressful, fearful, and stressed-out (as rats whose mothers did not lick and train them become).
B．Child abuse and even depression from mother, studies show, can do to people what careless rat mothers did to their pups: silence the stress-hormone receptor in the brain. In the brains of people who were abused as children and later took their own lives, the gene for the stress-hormone receptor is more likely to be "off" than it is.in people who did not kill himself or were not abused, found a 2009 study. In people, as in rats, when this gene is silenced, the stress-response system is around the corner, it extremely difficult to cope with life’s difficulty, leaving the person more liable to kill himself. In newborns of depressed or anxious mothers, a 2008 study found, this stress-hormone-receptor gene also tends to be silenced. That would put the children, like the rats’ pups, at risk of growing up to be hyper-sensitive to, and unable to cope with, stress.
C．The new study shows that childhood experiences that fall well short of abuse, or even of having a mother who is depressed, leave their marks on our DNA. Led by Marilyn Es, professor in the Department of Psychiatry and director of the Life Stress ＆ Haman Development Lab of the University of Wisconsin, Madison, scientists gave question papers to hundreds of parents, who were part of a years-long study, when their kids were infants and again when they were 3.5 and 4.5 years old. The questions asked about depression, financial stress ("how much trouble do you have paying monthly bills"), parenting stress ("do you often feel angry with your child"), and feeling strong ("do you feel pulled apart by all your obligations"). When the kids were 15, the scientists yzed their DNA, using cells obtained by cheek.
D．The scientists found hundreds of differences in the DNA of kids whose parents were in the top 20 percent of stress they will report in an upcoming issue of the journal Child Development. After applying a precise statistical instrument to make sure any "hits" were not random success, they found that mom’s high stress during the children’s infancy altered 139 genes, while dad’s stress during the children’s pre-school years altered 31 genes. Curiously, mom’s stress during the pre-school years, and dad’s stress during his kids’ infancy, had no genetic effects, perhaps reflecting how dads become more involved once their kids graduate from breast feeding. In another interesting finding, although mothers’ stress affected both daughters and sons equally, fathers’ stress had more effect on daughters than sons. That accords with the findings that when dad is emotionally or physically absent, girls tend to enter adolescence earlier and develop difficult temperaments, while boys do not.
E．The on-off status of genes in cells scd from the cheek may not be identical to the on-off status of genes in brain cells. The point, says Es, is not to identify the specific genes that parental stress changes, but to establish a fundamental principle: that the pathway by which parental stress affects children physically, emotionally, and traces back through our DNA.
F．What might be the impact of these genetic changes If they affect fundamentals of brain development, it may be permanent; although the brain retains enormous powers of plasticity, the window when the basic wiring takes place tends to slam shut by early hood. In other words, some DNA changes, particularly those in genes that dancing movements brain development, may have a lifelong fortune. But that "may" is crucial. Just as parental stress can alter DNA for the worse, later experiences might alter it for the better. That is at the top of Es’s to-do list: identifying the influences that can undo the harmful genetic and other effects of parental stress. Of course, prion is more effective than treatment. Kids Pick Up on Everything: How Parental Stress Is Toxic to Kids, a forthcoming book by family therapist David Code argues that the best thing parents can do for their kids is reduce their own levels of stress.
G．Since we already know that parents’ marital and financial stress can hurt children’s development, people bearing doubtful ideals might ask whether the new study advances the ball. It does. By showing how parenting exerts the effects it doe-namely, by altering which of a child’s genes arc turned on and which are turned off-it makes those influences much more real and concrete, much the way brain imaging studies that show addicts’ brains when they desire for heroin made addiction much more real and concrete: just as an addict can’t simply summon the willpower to kick his addiction, so a child cannot just shake off the legacy of a troubled infancy and adolescence. That legacy has altered her very DNA.
How Stressed Parents Affect Their KidsOnce genetic changes affect fundamentals of brain development, it may last forever.