Children exposed to stress have long-term changes in key brain areas, new study shows.

The study, conducted by researchers at the University of Wisconsin-Madison, early-life stress due to poverty, abuse or neglect can alter brain areas dedicated to learning, memory and emotion. These changes in the brain could lead to future health as well as relationship problems.

Every year, 1.25 million children are abused or neglected in the United States. Related studies have shown that abuse can lead to several genetic changes in children.

"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," said Seth Pollak, co-leader of the study and UW-Madison professor of psychology.

According to Pollak, early life stress can lead to depression, cancer, anxiety and heart disease. "Given how costly these early stressful experiences are for society ... unless we understand what part of the brain is affected, we won't be able to tailor something to do about it," he added.

The study was based on data from 128 children, aged around 12 years. The participants had experienced physical abuse, neglect or poverty.

Researchers interviewed parents and caregivers of the children and documented the participants' behavior. The team then took brain scans of the children and compared them with brain scans of other children growing up in middle-class families.

The team found that children exposed to stress had changes in the amygdale - a brain region associated with memory, decision-making and emotional reactions. Also, children who were growing up in a low-socioeconomic class had smaller hippocampal volume. Hippocampus is linked to consolidation of memory.

Why stress leads to long-term changes in the brain isn't clear. Researchers said that the findings of the study show that human brain is robust and adapts to the environment that it is in.

"Just because it's in the brain doesn't mean its destiny," said Jamie Hanson, one of the study authors, in a news release.

The study is published in the journal Biological Psychiatry.