Researchers have said that for kids, a little bit of stress provides a platform for learning, adapting and coping, however, a lot of it - chronic, toxic stress like poverty, neglect and physical abuse - can have lasting negative impacts.

A team of University of Wisconsin-Madison researchers recently showed these kinds of stressors, experienced in early life, might be changing the parts of developing children's brains responsible for learning, memory and the processing of stress and emotion.

These changes may be tied to negative impacts on behavior, health, employment and even the choice of romantic partners later in life.

Seth Pollak, co-leader of the study and UW-Madison professor of psychology, said, "We haven't really understood why things that happen when you're 2, 3, 4 years old stay with you and have a lasting impact."

For the study, the team recruited 128 children around age 12 who had experienced either physical abuse, neglect early in life or came from low socioeconomic status households.

Researchers conducted extensive interviews with the children and their caregivers, documenting behavioral problems and their cumulative life stress. They also took images of the children's brains, focusing on the hippocampus and amygdala, which are involved in emotion and stress processing. They were compared to similar children from middle-class households who had not been maltreated.

Hanson and the team outlined by hand each child's hippocampus and amygdala and calculated their volumes. Both structures are very small, especially in children, and study lead author and recent UW Ph.D. graduate Jamie Hanson and Pollak say the automated software measurements from other studies may be prone to error.

Indeed, their hand measurements found that children who experienced any of the three types of early life stress had smaller amygdalas than children who had not. Children from low socioeconomic status households and children who had been physically abused also had smaller hippocampal volumes.

The study has been published in the journal Biological Psychiatry.