Hormones produced and secreted in response to psychological stressors influence appetite and the drive to satiate that hunger. Epinephrine and corticotropin releasing hormone (CRH) are hormones that are released from the adrenals and hypothalamus (respectively) when we first encounter a stressor. They have an inhibitory effect on appetite (in other words, they suppress appetite). The role of these two hormones is to fuel up muscles so we can fight or flee from the (presumably life threatening) stressor. So this inhibitory effect makes sense: your body doesn't want you to pause for a snack when you should be running from the bear. (Smart body!)
In an ideal world, the stressor gets handled and removed. You process the stress and your body/mind/heart returns to a balanced state (aka eustress) and you go about your business. Your appetite returns to normal, signaling appropriate times to eat and not eat.
Now, if that stressor is persistent, a second wave of hormones is secreted. This time it's our buddy cortisol (released by the adrenal glands). In periods of prolonged stress, cortisol does the opposite of its first-wave compatriots - it increases appetite. Cortisol also is a hormonal motivator, so not only is your appetite stronger but your desire to eat is also increased with chronic stress. This shift is presumably protective, because no one can put up a good fight or run any distance at full speed for long without refueling.
These three "stress hormones" are really important players in the adaptive nature of our stress response. They have historically done a really great job at keeping us alive in the face of imminent perils. (Thanks, guys!) When we put ourselves in a modern day example - say a global pandemic - many of us are likely experiencing persistent stress, living in a cortisol bath that drives us to the pantry to soothe our worries day after day.
In terms of the relationship between stress and appetite (and the drive to satisfy it with chips and guac), there's more at play.
Ghrelin is often talked about a the "hunger hormone" because when secreted by the stomach it tells the brain to find something to eat. Ghrelin also plays a role in taste perception, reward behavior and reward recognition, among other things. It also has an anti-depressant effect, which may help balance out the emotional strain of stressful experiences.
Epinephrine triggers the release of ghrelin as part of that first wave response to a stressor. Again, this is a highly adaptive response that gave our ancestors the drive to refuel after they got away from the bear. For us modern day folk, who are experiencing more psychological stress than life-threatening stress (the body can't tell the difference so the hormonal response is the same), our primary response is constantly being triggered. Epinephrine goes up in response to being stuck in traffic/dealing with an argumentative co-worker/navigating a distance-learning school year with your kid(s) while working from home...and ghrelin responds in full.
Dopamine has two big effects on the body in regards to stress eating. It makes us feel both rewarded (I did a thing!) and connected (My heart is soothed because I did the thing!). Even thinking about food stimulates dopamine's release in the brain, an effect that is further amplified by eating a tasty treat. The bigger the "reward" the bigger the dopamine bath, so you get bonus points for cupcakes and popcorn. Here's another cool/not cool thing about dopamine: it's adaptive. So one cupcake today is going to stimulate a dollop of dopamine that you'll need two cupcakes tomorrow to obtain.
To wrap this biology lesson up and put a bow on it, here's a summary of everything above:
When you encounter a stressor, whether it be life-threatening or not, it stimulates hormones that have a snowball effect that results in an increased appetite and motivation to eat. Eating relieves stress by inducing an anti-depressant effect on your body, making you feel accomplished and connected.
At this point you might be thinking, "but my friend/kid/partner has the opposite experience when stressed. They lose their appetite and motivation to eat!"
Everyone responds to stressors differently. Some people find it easier to return to eustress than others. Some people experience acute stressors over and over and over, but stay out of chronic stress. Some people live in chronic stress for prolonged periods of time. Additionally, dopamine receptors are more sensitive in some individuals than others, making the reward-seeking behavior (like emotional eating) more powerful.
To quote my current fan-girl obsession, Emily Nagoski, PhD "we're all made of the same parts, just arranged differently."
This is what makes us interesting and unique, and what makes personalized medicine and nutrition such important tools for understanding ourselves and caring for ourselves in loving and authentic ways.
Understanding the mechanisms that drive behavior help me understand myself better. I hope you find the same to be true and that this article gives you some objectivity for a topic that is often loaded with self-judgment. Here's the truth: you are not bad/weak/a failure because you stress eat (or don't). Instead, you are sensitive to a chemical storm inside you that rages every time your stress response is activated. You may be tempted to go on a diet or blame your eating habits for this. But if you are looking for the root cause of stress or emotional eating, it is the difficulty of returning to eustress. Developing your stress resilience is the key to changing that pattern. Without that, your body will seek out the easiest form of relief: more food.
There are several self-care practices you can use to get out of acute and chronic stress to return to eustress more effectively. Emily Nagoski, PhD and Amelia Nagoski, DMA write about this and ways to "complete the stress cycle" in their book Burnout, which Dr. Barrett and I recommend to our patients often. Read it!
In the meantime, come back to this article as often as you need to to get some emotional distance from what you are experiencing. Use this information as a mindfulness bell to practice non-judgment. That awareness will serve you when you are looking for relief in food and give you the perspective of knowing yourself better so you can care for yourself better.
Resources and Recommended Reading:
How stress can make us overeat. Harvard Health
Chuang, Jen-Chieh, Zigman, Jeffrey M. (2010). Ghrelin's Roles in Stress, Mood and Anxiety Regulation. Hindawi.