A loving childhood with involved parents is likely to result in a happier adulthood, researchers find.
By Jasminee Sahoye
The research has revealed that the increased risk following such childhood adversity is associated with sensitization of the brain circuits involved with processing threat and driving the stress response.
Also, research has begun to demonstrate that in parallel to this stress sensitization, 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, a relatively common form of childhood adversity where parents are persistently emotionally unresponsive and unavailable to their children,” explained first author Dr. Jamie Hanson.
“Importantly, we further showed that this decrease in ventral striatum activity predicted the emergence of depressive symptoms during this key developmental period,” he added.
“Our work is consistent with other recent studies finding deficient reward processing in depression, and further underscores the importance of considering such developmental pathways in efforts to protect individuals exposed to childhood adversity from later depression.”
This study suggests that, in some people, early life stress compromises the capacity to experience enthusiasm or pleasure.
“This insight is important because it suggests a neural pathway through which early life stress may contribute to depression,” said Dr. John Krystal, editor of Biological Psychiatry
“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. This preparation could help lead to early intervention.”
Another Duke University-led study has pinpointed how early childhood stress affects the adult brain’s response to rewards.
Their findings suggest a possible pathway by which childhood stress may increase risk of depression and other mental health problems in adulthood.
Many studies have connected early life stress to later mental health issues for adults but little is understood about the reasons for this connection. The new study used functional magnetic resonance imaging (FMRI) to examine the relations between early life stress and reward-related brain activity in adults.
Participants in the study were closely monitored beginning in kindergarten and then were scanned using brain imaging when they were adults. The participants were all part of the Fast Track Project, which in 1991 began tracking how children developed across their lives.
For this study, researchers focused on the levels of stress that 72 subjects were exposed to early in development. At age 26, the study participants completed an experimental game to assess how their brains processed rewards and positive feedback. The scientists focused on reward-related activity in an area of the brain known as the ventral striatum, measured using FMRI.
“We found that greater levels of cumulative stress during childhood and adolescence predicted lower reward-related ventral striatum activity in adulthood,” said study lead author Jamie Hanson, a postdoctoral researcher at Duke’s Centre for Child and Family Policy and the Duke Department of Psychology and Neuroscience.
Hanson and colleagues found that early stress, specifically between kindergarten and Grade 3, was most strongly associated with muted responses to rewards in adulthood. Previous studies have identified this type of brain activity as a marker for increased risk of depression and anxiety.
“In participants with the greatest levels of early stress, we saw the lowest levels of activity in the ventral striatum in response to a reward,” Hanson said.
“We think reward-related ventral striatum activity is an important marker of mental health,” Hanson explained.
“Past studies have focused on the processing of threat and negative emotion after early stress. Generating positive emotions may potentially buffer some of the effects of stress.”