Stress

Deconstructing the Neurobiology of Resilience

Neuroscience explains why some people adapt better to stress and are resilient.

Posted Sep 06, 2016

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Source: CLIPAREA l Custom media/Shutterstock

The neurobiological underpinnings of resilience are dynamic and complex. In one of the most comprehensive and thorough neuroscientific reviews of how individuals adapt to stress, researchers at King’s College London (KCL) recently compiled a meta-analysis of dozens of studies that help us better understand the neurobiology of resilience.

The September 2016 review, "Adapting to Stress: Understanding the Neurobiology of Resilience," was recently published in the journal Behavioral Medicine.   

In this review, the researchers examine the interplay between various hormones, neuropeptides, neurotransmitters, and neural circuits associated with resilience versus vulnerability to stress-related disorders. The researchers' goal was to catalog how various mechanisms in our bodies—and specifically our brains—work in concert to make someone more or less "stress-resilient" across his or her lifespan. 

Because the neural mechanisms that underlie our resilience to stress are so multifaceted, the team decided to focus solely on the biological stress responses known to be linked with resilient phenotypes and how their enhanced neurobiological response to stress is processed.

While not part of this review, multiple studies have identified that factors such as social support, personality, temperament, and physical fitness play a pivotal role in levels of resilience. Although this particular review didn’t include studies concerning psychological factors, character traits, and lifestyle choices related to resilience, the authors emphasize:

“It should be noted that active coping strategies, humor, hardiness, and extraversion can promote resilience through fostering feelings of mastery, commitment, and competence as well as the ability to help others through bonding. Importantly, the propensity of resilient individuals to express positive emotions, in relation to negative events, enables them to control their anxiety and fears.”

A wide range of studies have found that positive social support and a strong face-to-face social network are key to psychological well-being. Additionally, various studies have reported that someone's level of social support can reduce and/or exacerbate the impact of post-traumatic stress disorder (PTSD) and/or major depressive disorder (MDD).

Deconstructing the Neurobiology of Resilience

John Gomez/Shutterstock
Source: John Gomez/Shutterstock

In deconstructing the neurobiology of resilience, this review had three main objectives. First, the KCL researchers wanted to understand the dynamic connection between stress and resilience, as well as, what differentiates a resilient from a non-resilient individual.

Second, they wanted to identify the neurochemicals, genetic, and epigenetic mechanisms thought to be the neurobiological foundation of resilience or vulnerability to a stress-related disorder.

Third, they wanted to understand whether the ability to cope with high levels of stress is innate, inborn, inherited, and/or acquired through specific training (e.g., through a stress inoculation process) or the result of some combination of all of the above.

The extensive search for this meta-analysis was conducted by the researchers between February 2014 and June 2014. Relevant studies published in peer-reviewed journals were identified through electronic queries via PubMed, Web of Science, Embase, and PsycINFO databases.

What Makes Some People More Resilient Than Others?

The researchers hope that presenting this vast body of knowledge will lead to a more finely-tuned understanding of the neurobiological components of a “stress-resilient profile.” Individuals who are classified as stress resilient tend to exhibit an enhanced capacity for avoiding detrimental physiological and psychological consequences as a result of exposure to extraordinary levels of stress.

There is significant variation in the way individuals react and respond to various levels of stress and adversity. Whereas some individuals will develop psychiatric conditions such as PTSD or MDD after exposure to toxic levels of stress, others seem to be Teflon coated and bounce back from stressful experiences without displaying significant symptoms of psychological ill-health.

The experience of extreme or prolonged stress doesn't automatically result in mental health problems. Therefore, the million-dollar question is to find scientific evidence that explains why some individuals are able to overcome unbelievable stress and hardship, while others’ lives are completely derailed by intense levels of stress. 

It's important to mention that resilience is not conceptualized by the researchers as the absence of a diagnosable psychiatric condition, but rather a constructive adaptation to adversity and traumatic experience.

The KCL researchers hope that putting together this comprehensive review will expedite the identification of underlying neurobiological components related to resilience. This could lead to improved methods and interventions to prevent and treat stress-related disorders.

The Link Between Eustress, Distress, and Resilience

Stress triggers physiological and psychological reactions in your body, brain, and mind in response to some type of “stressor.” This response is commonly known as "fight-or-flight." Generally, different types of stressors can be perceived in a positive light as being 'challenging' or 'threatening' if they are perceived in a detrimental way. 

The "fight-or-flight' mechanism is part of the general adaptation syndrome defined in 1936 by Canadian biochemist Hans Selye of McGill University in Montreal. Selye published his revolutionary findings in a pithy seventy-four-line article in the journal Nature, in which he talked about eustress (good stress) and distress (bad stress) as well as the three stages of general adaptation syndrome.

Once the bugle has sounded, and the stress-response troops are mobilized in the sympathetic nervous system...there has to be some type of recalibration of your stress hormones to regain homeostasis.

Of course, we need good stress in our lives; without it, we wouldn’t have the oomph to wake up in the morning and seize the day. But all of us need to harness the bad stress in our daily lives. One of the most simple ways to do this is to engage the "tend-and-befriend" mechanisms of the parasympathetic nervous system through social connections.

When stressful challenges are perceived as exhilarating and manageable—it creates healthy eustress. For example, successfully overcoming obstacles and adversity via athletic challenges is a classically rewarding experience that leads to feelings of accomplishment.

The daily athletic process creates an upward spiral of confidence and chutzpah. Conversely, threatening life-or-death experiences outside the athletic arena—that are overwhelming and appear to impose significant danger—can result in short-term or long-term physiological and psychological damage. 

Obviously, your brain is the central organ responsible for how you handle the stress response. It processes perceptual information for potential threats and initiates appropriate responses. Your brain and nervous system also regulate the physiological and/or psychological responses that end up either being adaptive or damaging. 

John Gomez/Shutterstock
Source: John Gomez/Shutterstock

The brain establishes a two-way communication as part of a feedback loop between itself, the immune system, and cardiovascular systems via endocrine and neural mechanisms during the stress response. By examining how humans and animals adapt to highly aversive environments (like combat), researchers have recently pinpointed specific neural, neurochemical, genetic, and epigenetic components that may characterize different levels of vulnerability, or resilience, based on how an individual responds to bad stress. 

A measured physiological response to environmental stressors is an evolutionary advantage as a function of the acute stress response, more commonly known as the “fight-or-flight” mechanism. However, if your recovery from a stressful situation is not accompanied by an adequate homeostatic response, the initial response could ultimately result in harmful after effects.

Toxic Stress Levels During Childhood Undermine Long-Term Resilience

A groundswell of empirical evidence suggests that cumulative environmental stress over the life cycle often increases an individual's risk for having a stress-related psychiatric injury. However, sometimes childhood adversity creates a more stress-resilient brain. 

That said, both human and animal studies suggest that experiencing severe stress in early life has a negative impact on the healthy development of someone's stress response system. Childhood trauma can cause long-lasting mental health problems into adulthood. 

Prolonged activation of the stress response system during childhood is considered "toxic stress." This is caused by such things as physical/emotional abuse, chronic neglect, or constant exposure to violence. Toxic stress disrupts the normal development of the brain and related systems. This increases the risk of stress-related disorders in adulthood. 

Studies that evaluated parental neglect and abusive behavior toward children during the early weeks of life found: fewer stress management skills, lower self-independence, and higher levels of anxiety and stress. Statistically, the more stressful and/or adverse experiences someone encounters in childhood, the higher his or her risk of developing cognitive, emotional, and psychiatric problems in adulthood. But again, this isn't always the case.

The latest review from King's College London points out that this was reflected in increased HPA axis and CNS activity when the same individuals were subjected to stressors in later life. Additionally, experiencing early-life toxic stress levels often led to hyper-functioning of Norepinephrine system, reduction in the hippocampal volume, and amygdala responsiveness to negative facial expressions.

Believing You Have a Degree of Control Negates the Power of a Stressor

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Source: Romolo Tavani/Shutterstock

Interestingly, the KCL review points out that research in human and animal models suggests that unexpected factors can play a pivotal role in determining whether an early childhood traumatic experience results in vulnerability to stress or resilience.

One of the factors known to play an important role in these circumstances is the degree of control that an individual has over the stressor. Another factor is the possibility of being able to change your situation. Personally, after reading this research, I realize that one reason being trapped at a stodgy boarding school during my parents' divorce was so traumatic was that I didn't have any control. I was completely powerless to change my geographic isolation or to physically escape.

The good news is that individuals can learn resilience through experience and hardship—in particular by developing qualities that facilitate appropriate coping strategies, adaptation, and recovery from stress. I figured this out in 1983 when I was 17. Coincidentally, the Walkman had just been invented, which was a godsend. I began running religiously to a mixed tape of Madonna's first album and Bruce Springsteen's Greetings from Asbury Park. This daily routine allowed me to escape psychologically and saved my life.

As a teenager, I learned through sports training how to create a place inside me that was always safe. This inner haven is surrounded by Kevlar coated one-way glass—I can see out, and I can feel all the emotions inside—but nothing can touch me or hurt me when I'm inside this asylum unless I decide to let it in. Otherwise, the stressors are deflected, and nothing can penetrate that fortress. 

The latest empirical evidence corroborates this anecdotal example and shows that encountering and overcoming stress-inducing situations may have a beneficial effect on resilience throughout your lifespan. Learning to navigate adversity early on can fortify a resilient disposition, particularly over one's perception of control and sense of stress mastery.

For me, the combination of aerobic exercise, sweat, musical anthems, and finishing a challenging workout, took away my feelings of learned helplessness and made me feel like I was the ruler of my destiny. It also created a neurobiological elixir that was a prophylaxis for many types of bad stress. 

Stress-Inoculation Can Immunize You From Distress

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Source: mavo/Shutterstock

In the latest review, the researchers speak about the concept of “stress inoculation,” which happens when an individual acquires an adaptive stress response to the negative effects of stressors. Stress inoculation is a form of immunity against predictable stressors that might occur in the future. Mindfulness meditation can be used as a stress-inoculator. The term is purposely analogous to vaccine-induced immunity against a virus.

Interestingly, animal studies tend to support the stress-inoculation concept and show that early-life exposure to the right dose of stressful events may actually protect against future hypersensitivity to stress. These findings suggest that overprotecting offspring or being a helicopter parent may backfire. 

One study evaluated the contribution of early stressors in the emotional stability of small rodents. The researchers randomly exposed a group of infant rats to intermittent foot shocks. This taught them how to elicit evasive movements to avoid the stressor. Another control group of infant rats were coddled and never experienced stressful foot shocks, which made them complacent.

When the two groups of young rats were put into an unfamiliar and novel stressful situation, those who had been intermittently subjected to stress displayed an enhanced coping response and a lower stress response.

There is one caveat. Because individuals have different stress thresholds, a stressor that may promote resilience in one individual could result in increased vulnerability in another individual. It's a thin line between learned helplessness and stress inoculation due to all the untold variables of individuals in their neurobiological, psychological, genetic, and epigenetic underpinnings.

Orchid Children vs. Dandelion Children

In a previous Psychology Today blog post, "How Do Genes Sway the Sensitivity or Resilience of a Child," I wrote about research which found that genes and epigenetics can cause a child to be hypersensitive like an orchid, or resilient like a dandelion. 

The latest meta-analysis confirms that genetic factors interact with neurobiological and epigenetic factors in ways that affect the biological characteristics and regulation of neurochemical receptors. Also, environmental factors produce epigenetic alterations within individuals, which influences resilience to stress or risk of a psychiatric condition.

Monkey Business Images/Shutterstock
Source: Monkey Business Images/Shutterstock

Additionally, there is more and more emerging literature which suggests that a positive social support environment can moderate individual environmental and genetic vulnerabilities and increase your resilience.

Our growing understanding of resilience leads us to consider how each individual can begin to establish a resilient profile. Again, these processes are complex and require a personalized and unique approach. 

For example, the neurobiological concept of resilience can't be narrowed down to a single neurochemical, hormone or peptide but rather is the result of the interaction of multiple chemical elements working in concert throughout complex networks within the human brain.

Also, the researchers warn that further complications arise in relating neurobiological processes to psychological states under the overarching concept of resilience. For example, a particular neurochemical may be found to be co-present with psychological symptoms of stress or resilience however this co-presence may not be sufficient to establish direct causation. Ultimately, more research on the neurobiology of resilience is needed. 

Conclusion: Nurturing the Neurobiology of a Stress-Resilient Brain for Life

 Maridav/Shutterstock
Source: Maridav/Shutterstock

In our topsy-turvy and unpredictable world, identifying effective ways to reduce stress and increase resilience has become a mandate for people from all walks of life, ages, professions, and socioeconomic backgrounds.

Fine-tuning the causal influences that create a stress resilient profile will be especially useful for those who operate in high-stress environments professionally. First, in relation to the successful completion of the given task, such as being a combat soldier, and secondly in relation to the individual's post-task physical and psychological well-being, as a veteran. 

Hopefully, in the near future, based on the insights gained from the latest King's College London review, an interdisciplinary approach will emerge that explores how neurobiological, genetic, epigenetic, and personality traits (as well community and group interactions) might work to facilitate the soup-to-nuts development of a stress-resilient profile. This could bring us one step closer to the prevention and effective treatment of stress-related psychiatric conditions such as PTSD and MDD. Stay tuned!

To read more on this topic, check out my Psychology Today blog posts, 

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