New York, Nov 8 (IANS) : Early life stress is a major risk factor for later episodes of depression and people who are abused or neglected as children are almost twice as likely to experience depression later in life, says a new study.

There may also be diminished processing of reward in the brain and associated reductions in a person's ability to experience positive emotions.

Researchers at Duke University and the University of Texas Health Sciences Centre at San Antonio recruited 106 adolescents, between the ages of 11-15, who underwent an initial magnetic resonance imaging scan, along with measurements of mood and neglect.

The study participants then had a second brain scan two years later.

The researchers focused on the ventral striatum -- a deep brain region that is important for processing rewarding experiences as well as generating positive emotions -- both of which are deficient in depression.

"Our analyses revealed that over a two-year window during early to mid-adolescence, there was an abnormal decrease in the response of the ventral striatum to reward only in adolescents who had been exposed to emotional neglect," said first author Jamie Hanson.

Emotional neglect is a form of childhood adversity where parents are persistently emotionally unresponsive and unavailable to their children, researchers said.

This study suggests that, in some people, early life stress compromises the capacity to experience enthusiasm or pleasure.

"This pathway might be targeted by neural stimulation treatments. Further, it suggests that survivors of early life trauma and their families may benefit from learning about the possibility of consequences that might appear later in life," said John Krystal, editor of Biological Psychiatry where the study appeared.