jeudi 1 octobre 2015

How Childhood Stress May Lead To Disease Later In Life

How Childhood Stress May Lead To Disease Later In Life

What are the childhood origins of adult disease? Might there be certain developmental periods in a child’s life when he or she is particularly vulnerable to stress? And might psychological distress early in life lead to heart and other health problems later in adulthood, even after that stress is gone?

A recent study on early childhood stress published this week in the Journal of the American College of Cardiology doesn’t definitively answer these questions. But it does suggest that a high level of psychological distress in childhood may lead to a heightened risk of disease in adults, even if the stress doesn’t linger on.

The study, led by researchers at the Harvard School of Pubic Health, concludes:

Psychological distress at any point in the life course is associated with higher [cardiovascular and metabolic disease] risk. This is the first study to suggest that even if distress appears to remit by adulthood, heightened risk of cardiometabolic disease remains.

An editorial accompanying the study notes “the possibility that there are sensitive periods in childhood during which some seemingly irreversible physiological, emotional, or behavioral processes are established that affect [cardiometabolic risk]. That is, perhaps there are critical windows of risk linking childhood distress and [cardiometabolic risk] that point to windows of opportunity for intervention.”

The new study was based on an analysis of data from the 1958 British Birth Cohort Study, a longitudinal look at people born in Great Britain during a single week in March 1958. Individuals completed measures of psychological distress and a biomedical survey when they were 45 years old after repeated assessments over the course of their lives, from age 7 to 42.

I asked the new study’s lead researcher, Ashley Winning, a postdoctoral research fellow in the Department of Social and Behavioral Sciences at the Harvard T.H. Chan School of Public Health, some followup questions. Here, edited, are her answers:

RZ: In this study were you able to determine what, exactly, constituted “stress” for these children? Trauma, illness, abuse? If not, might you speculate on what types of stressors might be linked to later heart problems?

AW: High levels of distress in childhood may be the result of early life adversity (such as trauma, illness, abuse, neglect, poverty) and this may be one reason children in these environments are at heightened risk of poor health. However, symptoms of distress may be in response to less dire exposures too – chaotic environments, parental discord, stressful circumstances – normative responses to difficulties that may become chronic in the absence of appropriate adult capacity to help the child learn to navigate these challenges.

It’s also possible symptoms of distress are early signs of an underlying mental disorder in childhood (which may or may not have a hereditary component). We suspect that distress occurs in response to a range of difficult circumstances but what other research has suggested is that ongoing distress is less likely to occur when there is a nurturing adult or supportive environment available.

In this study we did not look at what leads to symptoms of psychological distress, but rather the distress symptoms themselves. We used the term “distress” to imply a reaction to potential stressors (stressful experiences or events), as opposed to the stressors themselves.

Psychological distress in childhood was captured by symptoms of internalizing (e.g., depression, anxiety) and externalizing (e.g., conduct disorder, hyperactivity) disorders, which were reported by the children’s teachers. In adulthood, adults reported on their own symptoms and levels of distress.

Can you explain more about the possible mechanisms that might be contributing here?

Psychological distress may impact risk of heart disease, stroke, and diabetes in a number or ways, primarily through behavioral and biological pathways. For example, distress may motivate harmful behaviors such as cigarette smoking and physical inactivity, or reduce educational and occupational achievement. Given there are sensitive periods for establishing behavior patterns (e.g., smoking is typically initiated in adolescence), childhood and adolescent distress may be especially influential. So for example, kids who are highly distressed may be more likely to begin smoking cigarettes, and that habit, once begun can be difficult to change.

Psychological distress may also have a more direct biological impact on health by causing increased activation of stress-related biological systems (for example more sympathetic nervous system activation). Chronic activation of stress-related biological responses, triggered by repeated or sustained exposure to stressful experiences, can lead to a cascade of deleterious effects on processes related to heart health, including, for example, blood pressure and cholesterol.

If stress response systems are altered in childhood it may make people more reactive to stress and more prone to its cumulative effects over time. This is consistent with the concept of biological embedding, whereby early experiences are thought to “get under the skin” to influence human biological and developmental processes. Alterations in biological stress-regulatory systems that emerge early in life may become more difficult to rewire in adolescence or adulthood.

In our study, both behavioral and biological pathways appear to be relevant. Though we did not test this, it is also possible that social attitudes and stigma against those with mental disorders or a lack of empathy for individuals who are struggling, as well as insufficient resources to address their needs, contribute to these effects.

Are any of the findings surprising to you?

The most striking finding in our study was that high levels of childhood distress predicted heightened adult disease risk, even when it did not appear that these high levels of distress persisted into adulthood. This is the first study to suggest that even if distress appears to remit by adulthood, some heightened risk for diseases such as heart disease, stroke, and diabetes remains. We were surprised to see that severity of distress in childhood seemed even more important than severity of distress in adulthood in predicting adult disease risk.

What are the key implications of the study, and where do you go from here?

Our findings have several implications:

•Greater attention must be paid to psychological distress in childhood. It is an important issue on its own right and may also set up a trajectory of risk for more rapid development of adverse physical health outcomes as people age.

•Focusing on early emotional development and helping children learn to regulate emotions effectively may be an important target for disease prevention and health promotion efforts.

•Physicians should be aware of the impact of mental health on physical health. In considering disease risks, health professionals should look beyond health behaviors and inquire about current distress symptoms as well as history of psychological distress across the lifespan.

•Overall, our findings point to childhood distress as relevant for both screening and intervention related to adult heart disease prevention, and provide support for the importance of attending to early emotional development as an early prevention strategy.

Next steps:

We’re starting to look at disease risk biomarkers earlier in the life course (in childhood and adolescence) to see how early the association between distress and heart disease risk may become evident, and whether those effects are sustained over time.

We also want to explore positive and protective factors that might reduce risk, and to help inform the development of good prevention and intervention practices for improving psychological wellbeing (particularly in childhood, but also all across the lifespan).

What does all this mean for parents today thinking about stress in their children’s lives?

While many experiences or circumstances are not directly within a parent’s control, parents and caregivers can work to limit children’s exposure to highly distressing experiences and can also focus on teaching children healthy ways to manage and cope with stress, and on providing them with support in difficult circumstances. They can also be aware of and monitor children’s mental health (including symptoms of depression, anxiety, hyperactivity and conduct disorder) and be aware that seeking help earlier rather than later is important.

One note: Having a difficult childhood in no way guarantees higher disease risk as an adult. In our study we looked at the presence or absence of high distress but we did not look at positive or protective factors. Thus, it is possible that people who had a difficult childhood but who had positive resources available as they grew up, got into more a more positive supportive environment later on, had strong social support, or other positive experiences in adulthood or perhaps even obtained therapy, may not in fact experience excessive disease risk. As noted earlier, this is something we would like to look at more directly in future work.

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