Stress and neglect at home take an obvious toll on kids as they grow up. Many decades of research have documented the psychological consequences in adulthood, including struggles with depression and difficulties maintaining relationships. Now studies are finding that a troubled home life has profound effects on neural development.

Kids' brains are exquisitely sensitive. Even sleeping infants are affected by family arguments, a new study concludes. Researchers at the University of Oregon showed with functional MRI scans that infants from families who reported more than the usual levels of conflict in the home were more sensitive to aggressive or angry voices. While asleep, these babies had an uptick in brain activity in response to sentences read in an angry tone of voice, with most of the activity clustered in the parts of the brain responsible for regulating emotions and stress.

“Infants are constantly absorbing and learning things, not just when we think we're teaching them,” says Alice Graham, a doctoral student who led the study, forthcoming in the journal Psychological Science. “We should expect that what's going on in the environment is literally shaping the physical connections in their brains.”

As with family fighting, neglect leaves no external marks but powerfully affects the architecture of the brain. A Yale University study of teenagers found evidence using MRI scans that neglect and emotional abuse during childhood reduces the density of cells in emotion-regulating regions of the brain later on. The teens in the study did not meet the criteria for full-blown psychiatric disorders, according to the paper published in 2011 in the Journal of the American Medical Association, yet many experienced emotional problems such as impulsive behavior and risk taking.

Even well into adulthood, the effects of neglect are dire. A survey of adult patients at Chicago's Rush University Medical Center found that emotional neglect in childhood seems to increase a person's risk of stroke as they get older. The mechanism behind that increased risk is unknown, according to the paper published online in September 2012 in Neurology.

Although young brains may seem easily damaged by neglect or stress at home, that damage is unlikely to be permanent if it can be treated in time, explains physician Hilary Blumberg, who led the Yale teen study. Recognizing that a teen's lack of impulse control might be a symptom of neglect-induced brain changes, for instance, could help social workers or medical professionals offer the right treatments. In the future some of those treatments might directly target the neurological changes. For example, regular exercise is shown to slow the loss of gray matter in the brain caused by aging; perhaps it could protect against neglect-related losses, too. Researchers hope that continuing to investigate the brain changes brought about by a troubled home life will ultimately provide ways to undo the damage at any point in life.