Stress

Can Childhood Stress Make You Sick?

How early adversity affects health

Posted Feb 19, 2016

This post was authored by Sohyun Han, Ph.D. candidate in clinical psychology at University of Southern California

Sohyun Han
Source: Sohyun Han

Growing up can be tough. From minor tumbles on the playground to witnessing domestic violence between parents, children face a wide range of potential challenges. But many people don’t realize that stressful experiences in childhood can affect your immune system and literally make you sick in adulthood. As increasing evidence has shown, early childhood adversity increases the risk for cardiovascular disease, cancer, diabetes, and even early mortality.

For the past two decades, the Adverse Childhood Experiences (ACE) Study has published numerous articles on the link between childhood adversity and the leading causes of death in the U.S. Researchers at the CDC and Kaiser Permanente assessed more than 17,000 people (ages 19 - 60+) who were enrolled with Kaiser Permanente in San Diego. Kaiser members responded to a short, retrospective questionnaire that asked about adversity during the first 18 years of life. Adversity included physical, psychological and sexual abuse and living with a family member with mental illness or a drug/alcohol use problem. Researchers also assessed history of heart disease, cancer, and stroke. What they found was a cumulative association between childhood adversity and poor health. That is, increased childhood adversity was associated with an increased risk for heart disease, cancer, lung disease and overall poor health. The risk doubled or tripled among those who reported 4 or more types of childhood adversity. Furthermore, these associations persisted even after accounting for factors such as age, race, socioeconomic status (SES), smoking and hypertension.

Why are childhood stress and health so strongly linked? The explanation might lie within the body’s stress response system. Every time you perceive stress, your body activates the “fight or flight” system to mobilize your body’s resources to take action. Your heart starts racing faster, your palms get sweatier, and your body releases cortisol, a hormone that increases your blood sugar level. While this system helps you survive, too much activation can lead to dysregulation – either through chronic overactivation or underactivation of the stress response system. Over time, these out-of-sync stress responses can tax your body’s ability to regulate itself. Researchers call the wear-and-tear of this constant balancing act “allostatic load”. The theory of allostatic load provides an elegant explanation for how adversity takes a toll on the body’s stress response systems over time. Children who experience chronic stress, poverty, and a harsh family environment typically show less healthy daily cortisol patterns and either amped up or blunted responses to stress. This is problematic because it shows inefficiencies in their stress response systems, which has implications for the immune system (more on this later).

So how does overactivating the stress response system lead to poorer health? Rena Repetti, a psychologist at the University of California, Los Angeles (UCLA), uses the metaphor of “meshed gears” to illustrate how this happens (see figure below). The body can adapt to occasional stress, but chronic activation leads to wear and tear of the body’s stress response systems and, eventually, long-term negative health outcomes. In part, activating stress response systems is a trade-off for development. When the body uses up its resources to fight stressors, there are fewer resources for growing and maintaining long-term health. Case in point, children exposed to very extreme conditions of neglect and isolation sometimes experience stunted growth until they are removed from their stressful environments – a condition known as stress dwarfism.

Repetti, Robles, & Reynolds (2011), used with permission
Source: Repetti, Robles, & Reynolds (2011), used with permission

As I mentioned, stress plays a role in immune system health. The immune system, as we all know, protects us from outside threats like viruses, bacteria, and fungi. One of the ways the immune system fights invaders is through inflammation, which increases blood flow and anti-microbial activity to injured regions. When we get sick from colds or upper respiratory infections, inflammation causes annoying symptoms like congestion, a runny nose, and sneezing. Research suggests that chronic stress enhances inflammation. Turns out that individuals raised in harsh families show higher levels of inflammation in adulthood than those from healthier families.

Remember how chronic stress leads to allostatic load, or inefficiencies in the stress response system? Cortisol helps reduce levels of inflammation. However, having chronically high levels of cortisol causes immune cells to be less sensitive to cortisol, which allows inflammation to go unchecked. Inflammation in turn is a risk factor for cardiovascular disease, type II diabetes, rheumatoid arthritis and other diseases. Prolonged stress can therefore set a foundation for a poorer immune system in the long run. Given all this, it makes perfect sense why childhood adversity leads to poorer health in adulthood. 

So what can we do about it?

Before you start to panic that your parents’ divorce will cause cancer, remember that health is complex and shaped by many factors. Genes of course play a big role – you are more or less likely to develop certain health problems depending on your genetic predisposition. There is also huge variability in how people perceive stress. Two children exposed to the same stressful family environment might perceive stress in very different ways: for example, Sarah may perceive her parents’ divorce as catastrophic, whereas Lauren takes her parents’ separation in stride. Remember, it’s the perception of stress that activates the stress response system. In terms of protective factors, parental warmth may buffer some of these negative health consequences. Among adults who were impoverished growing up, those who had warm and caring mothers showed less inflammation than their peers.

 Kinjeng Submiter, Creative Commons license
Source: Kinjeng Submiter, Creative Commons license

Even for children without warm and caring parents, all hope is not lost. Evidence from a landmark longitudinal study found that intensive daycare in early childhood was associated with better health outcomes 30 years later. Impoverished children who attended day care showed fewer rates of heart disease and metabolic syndrome compared to similar children who did not attend daycare. Though childhood adversity is associated with poorer health, it seems there are many points at which interventions can help decrease the risk. Given that childhood adversity is linked to diseases that are costly to treat, it makes sense to invest early on in reducing stress among families and supporting early childhood education

If you’re curious, the ACE questionnaire can be found here: http://www.acestudy.org/ace_score

References:

Fagundes, C. P., Glaser, R., & Kiecolt-Glaser, J. K. (2013). Stressful early life experiences and immune dysregulation across the lifespan. Brain, Behavior, and Immunity, 27, 8-12.

Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., ... & Marks, J. S. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults: The Adverse Childhood Experiences (ACE) Study. American Journal of Preventive Medicine, 14, 245-258.

McEwen, B. S. (1998). Stress, adaptation, and disease: Allostasis and allostatic load. Annals of the New York Academy of Sciences, 840, 33-44.

Miller, G. E., Chen, E., & Parker, K. J. (2011). Psychological stress in childhood and susceptibility to the chronic diseases of aging: moving toward a model of behavioral and biological mechanisms. Psychological Bulletin,137, 959-997.

Muennig, P., Robertson, D., Johnson, G., Campbell, F., Pungello, E. P., & Neidell, M. (2011). The effect of an early education program on adult health: The Carolina Abecedarian Project randomized controlled trial. American Journal of Public Health, 101, 512-516.

Repetti, R. L., Robles, T. F., & Reynolds, B. (2011). Allostatic processes in the family. Development and Psychopathology, 23, 921-938.

Taylor, S. E., Way, B. M., & Seeman, T. E. (2011). Early adversity and adult health outcomes. Development and Psychopathology, 23, 939-954.