A quick(ish) lesson about stress
think of it a Stress 101… without the exam at the end.
Let’s reset the way we use the word stress.
First, I need to acknowledge that the term has always been problematic. I’ll save a deep dive into the history of the term for a later post (with a dash of it below) but here’s a spoiler: the word stress was never a great choice.
When one of the fathers of the field, Hans Selye, first used the term ‘stress’ in the context of health, he came under fire for attempting to define a field of study that captured everything and nothing. One of Selye’s contemporaries snarkily remarked:
“Therefore, stress, in addition to being itself and the result of itself, is also the cause of itself.” — Dr. Ffrangcon Roberts
I mean…. He wasn’t wrong.
In an attempt to avoid the ambiguity of the word stress, stress researchers, myself included, tend to lean more on the terms ‘stressors’, ‘stress response’, ‘acute stress’ and ‘chronic stress’.
But these terms can also fall victim to ambiguity and circular logic:
Stressor = the internal and external stimuli that trigger a stress response
Stress response = the physiological and behavioral response to a stressor
Acute stress = when the response to a stressor is isolated or brief such that the physiological/behavioral changes associated with the response are considered beneficial for health and/or survival (also, what I refer to as the adaptive stress response)
Chronic stress = when the response to stressors is elevated, prolonged, or consistent in a way that the physiological/behavioral changes become detrimental for health and/or survival (I might refer to this as a maladaptive response)
Some of you may have heard (or personally use) the terms eustress and distress or even allostasis and allostatic load with the Allostatic Model as alternatives to redefine stress in an identifiable, quantifiable, actionable way. All have their own use cases and benefits and limitations. But, in the interest of avoiding that rabbit hole, I’ll bounce back to defining stress…
What is the stress response?
While I’m tempted to get deep into the weeds of the physiological cascades that stressors tip off and how all the systems in the body respond accordingly… in the interest of brevity (ha!), I’ll attempt to keep it simple.
Let’s start by considering the adaptive stress response. Put aside modern human stressors for a second and look at why the stress system exists in our brains and bodies to begin with: survival.
Say you magically transplant into the body of an ancient human relative cruising the savannah. You spot a lion in the bush ready to pounce.
Your brain interprets the situation – predator equals stressor – and cues an acute stress response.
At that moment, your brain triggers two key arms of the acute stress response. On a blink-and-you’ll-miss-it timescale, the fight-or-flight1 response activates the sympathetic nervous system to release catecholamines (adrenaline + noraderenaline). In the context of the lion, this response has everything you need to get up and go or stay and fight – increased blood flow to shuttle oxygen across your body, energy mobilization to feed your muscles. We all know the physical sensations that accompany that fast reaction – heart racing, palms sweating, mind focused. You have probably experienced the feeling when watching a car run a stop sign and narrowly miss you. And you’ve likely also felt it when getting up in front of a crowd to talk or jumping out of an airplane while skydiving. We, modern-day humans, relate to adrenaline in funny ways.
The slower arm of the acute stress response2 operates via hormones called glucocorticoids. In humans, the main glucocorticoid is cortisol (so I may reference this as the cortisol response, which, I know, will annoy some stress folks who prefer more precise terms).
Cortisol might ring familiar given that this hormone often gets the credit and blame as THE stress hormone (more on that one in a later post too). Since cortisol release does not get directly triggered by the nervous system but needs a whole signal cascade – a hormone to trigger a hormone to trigger a hormone – it takes a lot longer for this arm of the stress response to have an effect. Stress-induced cortisol becomes measurable in the bloodstream nearly three minutes after encountering a stressor and peaks 15-30 minutes after. Think of it as a game of telephone, kicked off by a whistle, that signals one person to instruct another person to write a note instructing you to slowly close your pointer finger and thumb around a piece of skin on the forearm of the person next to you… vs… just knowing to pinch the person next to you when the whistle blows.
When compared to the nearly instantaneous sympathetic nervous system response (the latter in that terrible analogy), the cortisol response is a slowpoke.
In the time it takes for cortisol to rise in your bloodstream, you have either successfully escaped the lion, fought off the lion, or been completely devoured. Which makes cortisol seem useless in this classic stressor context. However, it is not cortisol’s job to help you fight or flight.
Cortisol mops up the mess after the catecholamines wreak havoc on your system in the interest of immediate survival. Cortisol prepares the body for the next stressor. Cortisol gets you through your slow limp to safety and prepares you for when the lion decides to continue stalking. Cortisol acts in the interest of the body’s return to healthy balance and long-term survival and this is where cortisol connects with the reproductive system, immune function, metabolism, behaviors, etc. Cortisol pauses unnecessary processes and behaviors, diverts resources, changes functional priorities in the interest of long-term survival. These widespread connections between cortisol and nearly every system in the body is one of the ways modern-day humans get themselves into health-related trouble when it comes to stress, as discussed in the context of chronic stress below.
Here, I must point out and emphasize that, in the context of the Maternal Stress Project, ALL the stressors we will consider, their layers, their connections represent psychological stressors. Even when a node appears to have a physical component as well, for the purposes of this project, we are only exploring the psychological component – how the brain perceives, processes, and signals an external stressor rather than associated internal stressors.
A psychological stressor is the lion in the bush as a potential threat, not the actual, physical threat when the lion catches you. It is the stress response related to the external anticipation of the experience, not the internal response related to the actuality of that experience. For example, in the Maternal Stress Project map, food insecurity is a source of stress that can be considered both a physical stressor (hunger, malnutrition) and a psychological stressor (the concept of missed meals+hunger+malnutrition). In the context of this project, we focusing on the psychological stressor, narrowing in on how the brain interprets food insecurity and the related health consequences of that stress.
There is incredible variability in how individual humans respond to and are affected by stress, a result of the “psychological milieu” that external stressors filter through before the body responds. And this is where the opportunity for change comes in. I believe that classifying what makes a stressor a stressor while connecting as many dots as possible will open opportunities for new stress-related solutions at small and large scales.
But first, we have to define…
What makes a stressor a stressor?
How we see and interpret ‘lions’ in our environment determines how our bodies physically respond.
When is a lion a lion? More complicatedly phrased as: What are the characteristics of an external stimuli that stimulate a stress response? Especially when that stressor does not directly affect survival.
Decades of research have categorized a few key psychological factors that trigger a stress response: lack of control, unpredictability, novelty.
Lack of control – Stemming from research demonstrated that when you expose animals to the same repeated stressor (say, a foot shock) but give one set of animals control over that stimulus (access to a lever to turn off the foot shock), the animals with control respond less and experience reduced or no chronic stress effects.
Unpredictability – In similar experiments, when an animal knows precisely what a stressor will come around in their day, that same stressor stops initiating a physiological stress response.
Novelty – my super scientific summary: new things are scary. Another way to think of this is that novelty = misaligned expectations (which also feeds lack of control and unpredictability).
What makes a stressor not a stressor.
As you can probably imagine, the flip side of those key psychological factors – control, predictability, familiarity – have the opposite effect on how stressors are interpreted.
In addition, certain elements modulate the interpretation of an acute threat.
Animal research demonstrates that having an outlet for frustration – a rat running on an exercise wheel, a baboon pounding on a lower-ranking member of the troop – decreases the magnitude of a stress response.
A more human-centric stress response modulation tool is social affiliation. Strong bonds, friend and community support, reliable partnership all have some of the strongest effects on reducing a stress response. Social affiliation will pop up later in the context of stress buffering.
Perception matters
Humans are complicated animals. We feed external signals through more processing centers in our brain than nearly every other species. Our human brain interprets running late to school pickup as a ‘lion’ while also having the capacity to ignore the threat of an actual lion within a zoo enclosure.
One example of the contextual capacity to change perception: Are things getting better or worse? The school pick-up ‘lion’ might become less of a stressor (with a reduced stress response) if you receive a call from a friend who offers to pick up your kid for you. That same school pick-up ‘lion’ might become more of a stressor (with a greater stress response) if the school calls and your sad, forgotten kid screams for you in the background.
“The subtle and complex human correlates of the physiological stress response can be extraordinarily plastic. Stated more plainly, we have a heartening capacity to change.” – Robert Sapolsky
Tying back into the Maternal Stress Project – this is where connections between stressor nodes come in. The more connections or the stronger the connections or the more uncontrolled or unpredictable the stressor or connected stressors, the greater the health risk from an overall stress impact. BUT, when the load is lifted on connected stressors, when connections between stressors are weakened, when stressors occur with a perception of control or predictability, when stress buffers alleviate the gravity, the stress responses and the related health risk of the overall stress, can be reduced.
Not all or nothing.
If you feel your heart racing as you step up to a podium in front of a crowd, that feeling does not necessarily indicate that your body will also tee up cortisol release. In fact, different types of stressors result in different patterns of responses that operate separately via the nervous system versus the cortisol axis. A stress response is not all or nothing. It varies depending on the intensity of psychological factors.
The intensity of the psychological factors depends on how that external, potential stressor feeds through your complex brain, starting with perception. The brain considers contextual information, gauging if and how to respond, and then regulates cortisol release and recovery.
If your body does release cortisol, that hormone response comes in a variety of flavors: large spike or small spike, long spike or short spike, quick recovery or slow recovery, and everything in between.
As you might imagine, the body recovers with less of a lasting impact when the stress response is smaller and/or shuts off relatively quickly and all the affected systems return back to a pre-stress baseline.
Cumulative = Wear-and-Tear
Stress has a “death by a thousand cuts” issue too. Small stress responses can add up and impact health.
The body naturally seeks balance. In the context of a stressor, the systems that are activated and elevated have counterbalancing mechanisms that help them return to pre-stress baseline. When these systems are activated in a way that does not allow full recovery or are maintained at a stress level for an extended period of time, counterbalancing mechanisms shift in an attempt to get the body back to some form of balance.
Picture the balanced body as a seesaw. A few pebbles sit on each end. This body is in balance without too much weight on the seesaw. Now picture a seesaw where the pebbles keep piling up on one side and then more pebbles pile up on the other side to match. Individually, the pebbles do not weigh a whole lot. And the seesaw is still balanced. But, now there is quite a bit more weight on the board and the fulcrum. The balance is more precarious. The integrity of the board is weakened. That extra weight = wear-and-tear. (More on wear-and-tear in the context of chronic stress and health in the section below.)
In the context of stress-related wear-and-tear across a lifetime, I am fascinated by the concept of ‘weathering’ posited by Dr. Arline Geronimus.
"It's really about how much stress versus social support you get in your everyday life.
A lot of [stress] is simply everyday life: Coming home after night shift work and having to stay wide awake and vigilant so you don't forget to get off your bus for the next bus to go home. Trying to get your kids up for school at five in the morning so you can also get to work. ... This means that the stress hormones are chronically flooding your body. The fats and sugars that you catapulted into your bloodstream for energy are constantly flooding your body.
It means your heart rate is up, [and] like any other over-exercised muscle, you'll start to get an enlarged heart. You'll start to get hypertension from pushing so much blood through certain arteries and veins to get your heart rate going and your breathing going." — Dr. Arline Geronimus
The concept of weathering makes so much sense, especially in how to understand health disparities as they relate to the stress of discrimination and racism (spoiler: it’s not race, it’s racism) and other social determinants of health. Individuals who experience low levels of stress for their entire lives operate at a daily baseline that is closer to a chronic stress state, and, as a result, experience health complications at a higher rate.
Which leads to…
When does acute stress become chronic stress?
Clearly, the person who jumps out of airplanes for fun is not putting their life at risk because of the resulting acute stress response. As Bruce McEwen, a preeminent stress researcher once pointed out: it might be better to think about the difference between being ‘stressed’ and ‘being stressed out’. While acute stress is beneficial and healthy, chronic stress (being ‘stressed out’ or in allostatic overload for you allostasis folks) “serves no useful purpose and predisposes the individual to disease”.
Meaning: chronic stress = when you start seeing the health impacts of stressors… Or when you could see health impacts of stressors.
To stay in the seesaw analogy, chronic stress is piling up pebbles and/or stacking on a few large rocks – it’s added weight for an extended time, it’s increased instability, it’s slow wear-and-tear on the plank and fulcrum, weakening the balancing mechanisms. The health consequences related to tipping or breaking the seesaw with potential health implications related to the increased likelihood of tipping or breaking.
If it seems like I’m dancing around something here, I am. Stress gets tricky in a clinical context because “stress” isn’t really a clinical term. Stress is not an illness3. Stress does not even directly cause illness. No medical professional will diagnose you with stress, chronic stress, or even allostatic overload. Stress exists in the subclinical space.
“It is never really the case that stress makes you sick, or even increases your risk of being sick. Stress increases your risk of getting diseases that make you sick, or if you have such a disease, stress increases the risk of your defenses being overwhelmed by the disease.” – Dr. Robert Sapolsky
This distinction all too often makes the potential health effects of stress invisible – a body operating just below the surface of illness until one more pebble or rock tips or breaks the seesaw… or doesn’t. However, even without visibility, we cannot ignore a body at risk for negative health outcomes or that real opportunities exist to prevent that body from tipping over the edge into an unhealthy state.
Reevaluating and centering stress in a different way allows a more impactful view for risk analysis and preventive care. New opportunities for health solutions exist in the space separating external stressors and internal illness. Space between all the pieces: potential threats in the external world → the perception of those threats as stressors → the physiological stress response to the perceived stimuli → downstream targets that break when the system is overwhelmed by the frequency, magnitude, timing of the stress responses → pathologies resulting from those systems breaking. Preventive care must start upstream — addressing potential threats, perception, and modulation of the stress response.
For the Maternal Stress Project, revisiting the terminology and concept of ‘stress’ serves to acknowledge that we are all flirting with the line between healthy and unhealthy with regard to the stressors of American motherhood while recognizing that some of us have more weight on our seesaw than others. In addition, evaluating and aligning the basic science of stress physiology aims to give weight to solutions that ameliorate, diminish, buffer, and/or eliminate exposure to stress in our personal journey, our community, our medical system, our society, and everything in between. A universal shift of focus to extend ‘stress management’ in the context of health beyond personal responsibility and toward the structural, cultural, and systemic changes necessary to impact all birthing parents, all women, all mothers, all caregivers.
Quick summary of the key elements that will be relevant for the Maternal Stress Project:
It’s not all in your head – psychological stressors have real physical effects
The human brain is a complex beast – what is ‘stress’ to one person may not be ‘stress’ to the next
Perception is your filter
Context matters – the stress signal can be modulated up or down based on negative associations or positive ones
For modern-day humans with modern-day lions, the line between beneficial stress responses and harmful chronic stress is a fine one.
P.S. Here is another way to think about it for the more medically minded and my fellow “how kids” out there. The table below was adapted from one in this paper and informed by another put together for an article centered around stress+physiological changes during the perinatal period (a topic that I am truly fascinated by and will write more about soon)
I’d be remiss not to point out that the terminology and concept of ‘fight-or-flight’ came out of male-dominated research, which had a tendency to bias science in the masculine direction. The counter to fight-or-flight, argued that female animals respond with ‘tend-and-befriend’ behaviors when faced with a perceived threat. While I fully acknowledge that there are sex differences when it comes to stress physiology and behavioral responses, I don’t love the masculine/feminine gendering of the response imagery, especially when it comes to humans. Females have full capacity for ‘flight’ if faced with a predator and I know (from my own impulses) that a mother could put up a good fight if she or her children/offspring are threatened. On the flip side, males have the capacity to ‘tend’ (an area of neuroscience that has barely had its surface scratched… because of bias) and, similarly, ‘befriend’. It is critical to examine sex differences while also acknowledging the spectrum and considering the bias through which research findings are produced.
In lay descriptions of acute stress, I have seen the glucocorticoid response lumped in to reference a general the ‘fight-or-flight’ response. If it is helpful for your brain to categorize acute stress response = fight-or-flight response, go with it. Just remember, the glucocorticoid/cortisol response is not helping with the rapid response needed to fight or flight, it is helping with everything after the fighting and flighting.
The only clinical diagnosis with ‘stress’ in its name is Post Traumatic Stress Disorder… more on that in another post. For now, fun fact: cortisol, the stress hormone, decreases in cases of PTSD.
Thank you Dr. Dickens for articulating what I feel like I've been struggling with for years...
"A universal shift of focus to extend ‘stress management’ in the context of health beyond personal responsibility and toward the structural, cultural, and systemic changes necessary to impact all birthing parents, all women, all mothers, all caregivers."
This vague notion and societal narrative telling us all to just "manage your stress and you'll solve your health problems." But stressors don't magically melt away because you want them to because you wake up one day and decide that somehow you're now able to "manage" your stress, because most of these stressors are systemic in nature.
Dr. Gretchen Sisson also talked about this need at the Moms First Summit in NYC a few weeks ago (https://www.momsfirstsummit.us/). Dr. Sisson says "I think it's important to understand the ways that these aren't just individual decisions, because if we put the burden of holding this on each individual mother, each individual family to navigating your own path to having it all, right, then you miss the opportunity to make a collective call to action."
So I'm here for it. I'm here for the collective call to action to get us closer toward the structural, cultural, and systemic changes that we all need. I'm following your lead and the work of The Maternal Stress Project very closely...well done.
So interesting to read about what I knew because I lived it. This is why I couldn’t get pregnant when we had a struggling restaurant. I was testing my pH and it was chronically acidic. Until we closed our restaurant (had to after 9/11) and I was magically in balance. We closed our restaurant in April of 2002 and our son was finally born after six years of infertility in April of 2003.