High stress between 5 and 8 is biologically embedded, posing mental health risks decades later into adult life, suggests US brain scans study.
Brain scans have demonstrated a strong biological link between early life stress and poorer mental health. We have been able to highlight brain patterns in adults that seem to have been set in place by events that occurred 20 years previously.
Our findings suggest that experiences in early childhood have a long-lasting effect on brain development that parallels already well known effects on behavioral development. In short, bad experiences can become biologically embedded in the brains of young children and leave markers that are still observable decades later.
"Adults who had endured high levels of stress between the ages of 5 and 8 typically displayed less activity than normal in the parts of their brains linked to motivation, positive moods and depression. We didn’t find this pattern linked to stresses experienced between ages 9 and 12 or between 13 and 17."
Our study included 72 mainly African-American men, aged 26, in the United States who were known to have suffered high stress in childhood. Beginning when they were five years old, they and their parents had been interviewed annually about adverse events that had occurred in the previous year. So we knew, for example, when parents had developed drug problems or had mental health issues, and when there were family conflicts, divorces or chronic illnesses that significantly affected the family’s functioning.
Brain scans – neuroimaging – enhance the picture painted by behavioral studies
We already knew from research in California – the Adverse Childhood Experiences (ACE) Study – that children who experience a lot of these events are two or three times more likely to suffer depression as adults. We aimed to see whether brain scans could identify biological markers for such vulnerability.
The adults played a simple card game on a computer screen, in which they were asked to guess whether the next card would be higher or lower than five. A batch of wins gained them cash and praise. If they guessed wrong, they lost money and missed out on praise. Using an MRI scanner, we examined activity in the part of their brains – the ventral striatum – that is associated with motivation and positive mood. People who are prone to depression, for example, typically show uncommonly low responsiveness in the ventral striatum when they have a rewarding experience.
We found that men who had endured high levels of stress between the ages of 5 and 8 typically displayed less activity than normal in the ventral striatum when they won at the card game. Their brains showed patterns that were consistent with the reduced motivation, lower positive moods and depression that spring from such stress. This pattern wasn’t linked to stresses that the men experienced later in childhood, either between ages 9 and 12 or between 13 and 17.
Research should test younger children’s vulnerability to stress
These findings suggest that children are vulnerable to the long-term, biological impact of stress when they are under 8. We lacked data on stressful experiences for our subjects before age 5, but these younger children could be even more vulnerable. The next step should be to look at the brains of adults for links to stressful experiences that took place before they were 5. Our earlier research has already demonstrated that when children in this age group experience adversity such as severe poverty, the grey matter in their frontal lobes matures more slowly).
“This work might lead to better ways of understanding, treating and, ultimately, preventing the negative mental health consequences of early life stress. It would also provide a tool for testing interventions.”
Our findings from neuroimaging are consistent with previous research by Jack Shonkoff and colleagues at Harvard’s Center on the Developing Child, which found that early life stress is associated with compromised physical and mental development. Studies looking across multiple research findings also suggest that early life stress, such as abuse or neglect, is associated with a 68 percent increase in the incidence of anxiety and depression. These linkages have been well studied in psychology, epidemiology and other related disciplines, but our study throws light on the biological mechanisms behind them.
We still don’t understand the entire chain of causality between stress, biological change and behavioral alterations. However, continued work might lead to better ways of understanding, treating and, ultimately, preventing the negative mental health consequences of early life stress. It would also provide a tool for testing interventions.
Scanning can help develop precision treatment for mental health
Neuroimaging may also help to develop precision medicine in diagnosing and tackling mental health conditions. Diagnoses such as “depression” cover a variety of symptoms, suggesting that it comprises a complex of factors. A depressed person might lack motivation, experience less joy and enthusiasm, or have negative feelings such as sadness, guilt, or pessimism. Neuroimaging discrete parts of the brain associated with these different behaviors can help to disentangle these symptoms and lead to more individualized diagnoses and more personally tailored treatments, whose efficacy could potentially be checked using brain scans.
Our big hope is that, having isolated some of the biological impacts of stress on children, we will be able to intervene effectively very early to reverse those impacts, rather than await the onset of symptoms, possibly years later. Success will depend on the plasticity of the young brain – which seems to be considerable – and the effectiveness of the intervention. Neuroimaging could help us monitor which treatments have the most impact, so we can focus our resources on the best and most cost-effective practices.