Verified by 
Key points
- "Hanger" is a common experience, but only recently have neuroscientists understood why it comes about.
- The brain uses overlapping mechanisms to interpret emotions and body signals, helping keep us alive.
- Signals from the heart, lungs, gut, immune system, and many others influence emotions and mental health.
A recent study found that as you go about your day, the hungrier you get, the more irritable and angry you feel. For most, this won’t come as much of a surprise; science is just telling us what we already know. Feeling emotional when hungry is such a quotidian experience it even has its own portmanteau: "hangry."
But just because something is a common, everyday experience does not mean we fully understand where it comes from. What is it about the experience of hunger that makes it able to be confused with an emotion? And if hunger can be conflated with an emotion, why anger—why doesn't hunger evoke other emotions instead, like disgust ("hisgust")?
The answer to this question is a lot more complicated than it first appears—and, as I’ve written about in my book The Balanced Brain, it also reveals something essential about the nature of mental health.
You might assume hanger occurs because hunger is an unpleasant, stressful experience for the body (and brain). So naturally, undergoing it simply makes us feel emotionally worse. There is some truth to that explanation. Hunger can evoke similar biochemical signatures to negative emotional experiences, such as increased levels of cortisol in the bloodstream.
Or perhaps you wonder if feeling hangry occurs because our brain’s normal efforts to suppress negative emotion are temporarily weakened by lack of energy from food. There is an element of truth to this, too. But neither explanation is fully satisfying.
If it’s just about a temporary lack of energy, why then do most people report that even just realising that they are hungry rather than distressed—amidst an episode of hanger—alleviates their negative emotions? There is something far more interesting happening in the brain.
To unravel why our fascinating brain generates feelings like hanger, you need to consider why we have a brain in the first place. Brains are not mandatory: sea sponges have no brain or wider nervous system (jellyfish have a nervous system but no brain). Having a brain comes at a major energetic cost for an organism. Our brains expend hundreds of calories every day, accounting for about 20 percent of our energy needs despite their relatively small size (only 2 percent of body weight). But human brains are more than worth their cost.
Our brain keeps us alive—fed, watered, oxygenated, and so on—in the wake of ever-changing environmental needs. A constant stream of sensory information helps us stay abreast of potential threats to our survival. This enables our brain to rapidly and accurately perceive our bodily needs, and to compute what we need to do to avoid potential survival threats.
But not all threats to survival can be seen, or heard. Threats like hunger or thirst are conveyed to the brain from our internal, bodily environment, along with other information from our blood vessels, heart, lungs, immune system, and many other systems.
These very same survival signals from the body play a crucial role in our experience of emotions. If you started to feel breathless and felt your heart pounding fiercely in your chest, you might interpret these physical signals as excitement, or anxiety. Profound disgust is often accompanied by feeling sick to your stomach.
That is not to say that emotions are fully explained by bodily signals alone. Rather, our brain maps incoming bodily signals and depending on their patterning and context interprets them as different feelings. Similar physiological states in the body might be identified as either an emotion or a bodily signal by the brain, depending on other factors.
When you feel an emotion, any emotion, one aspect of what you are feeling is the sense of your body in that moment. Your brain is tasked with interpreting your body’s signals—detecting, predicting, and even modifying the information sent from your body. That is why a bodily signal, like hunger, can feel a lot like an emotion, like anger: because their overlapping bodily signals influence both our sense of an emotion and our sense of bodily needs processed in the brain.
Hunger is only one of many signals from the body that influence emotion. Changes to the body’s immune system such as heightened inflammation also change our emotional state, and may even cause mental health symptoms in some cases.
You might have experienced feeling "blue" after a flu or COVID vaccine. In the lab, the temporary inflammation caused by tetanus vaccines worsens mood, especially in people who show changes in a brain region known to be associated with depression called the subgenual cingulate cortex. People who take medication that dramatically increases inflammation (such as a hepatitis medication called alpha-interferon) develop a full major depressive episode in nearly half of all cases. In the other direction, many people with depression show chronically raised inflammatory markers in their blood. Reducing inflammation could even be an underexplored route to treating depression.
Hanger suggests that there is a blurry line between bodily states and emotions. This matters for mental health because it means that we cannot ignore the influence of our physical body—its signals, its health, or its illness—on our experience of mental health.
For many disorders, the line between physical and mental health is equally blurry: an arbitrary division that can even be misleading. Disorders traditionally characterised as mental health may come up as disrupted physiology in the body, such as in the immune system. Similarly, disorders that start with physical health changes, such as inflammatory and metabolic syndromes, could have important mental health consequences, potentially even driving symptom maintenance.
Hanger is not the exception but the norm. Our brain’s interpretations and predictions about bodily signals are not fixed, but dynamically updated with new information (e.g. remembering one hasn’t eaten yet today)—much to the relief of many experiencing hanger because eating a sandwich is often easier than figuring out the source of our negative emotions. The overlap between bodily states like hunger and emotions like anger is not a coincidence or a bug, but a feature of our nervous system, exploiting key survival signals for physical and emotional homeostasis in pursuit of a balanced brain.
Facebook/LinkedIn image: The Num Phanu/Shutterstock
