You feel a bit sick as your stomach tightens and your heart starts pumping like a machine gun. Your breathing becomes shallow and your muscles tense. The rest of the people at the dinner party are oblivious, chatting nonchalantly and enjoying their meals. Why does your body seem to be gearing up for an epic battle when there's no real danger in sight? This blog post briefly discusses the neurobiology of social anxiety, by taking a look at what actually happens in the brains and bodies of those who experience it.

What is fear, anyway?

If you have Social Anxiety Disorder (SAD), then you'll be familiar with the physiological signs of fear, some of which were mentioned in the introduction to this article. The fact that you experience this fight-or-flight response indicates that your primitive survival instincts are strong.  No one wants to feel sickly and shaky at a dinner party, but if you were facing up to a sabre-toothed tiger, being charming and witty wouldn't get you very far. This is why you start to breathe heavily as your heart pumps blood, hormones and adrenaline all around your body, tightening your muscles and providing you with a burst of energy to help you survive the danger.

This shows us that our brains are hard-wired for survival, allowing us to respond quickly and unconsciously to environmental threats. Our brains have been structured like this since our early ancestors roamed the plains. Nowadays the sorts of dangers that we typically face have changed, but the parts of our brains that kept us safe all that time ago have not. Modern day humans, however, have also developed a newer part of the brain called the cortex. This allows us to plan, reason and problem-solve. It is this which separates humans from animals and helps us to control the automatic responses emanating from the more primitive parts of our brain. 

What this means is that ‘anxious’ people actually have an evolutionary advantage. They would have been the most likely to survive back in the days of roaming predators and medieval battles. So this feature of anxiety, the fight-or-flight response, can be understood as an adaptive survival mechanism which is simply no longer as pertinent in modern times.

What happens in the brain when someone feels fear?

Out of the corner of your eye, you see something that looks brown and furry, vaguely like a bear. Your fight-or-flight reaction is triggered instantly, before you even have a chance to think. What has happened? First, the visual stimulus passes through your thalamus and into the amygdala. This is your brain's emotional centre and the ancient part that is responsible for responding to fear. The amygdala shouts 'danger!' and activates several parts of your brain and sympathetic nervous system, including the hypothalamus and pituitary gland. Next, your body is prepared for war (i.e. fight or flight) by flooding the blood-stream with a cocktail of hormones such as norepinephrine, cortisol and epinephrine (adrenaline).

Then, just as you were about to indulge the latter part of your fight-flight response by running for the hills, a new thought enters your mind, perhaps even on an unconscious level: “I live in the city. It’s quite unlikely that there would be a bear out here.” So you chance another glance at the approaching predator and notice, to your embarrassment, that it's just a friendly Labrador! Before you know it, your breathing and heart-rate are back to normal and you continue peacefully on your walk, giving the dog a pat on the head.

How was your brain able to calm you down in this way? When you told yourself that bears don’t live in the city, this was likely your pre-frontal cortex (PFC) speaking: the newer part of the brain that helps you evaluate information thoughtfully. So, unlike the jumpy amygdala, the rational PFC determined that this furry brown thing was likely harmless. Next, the PFC performed an important function by effectively calming the amygdala’s automatic fear response.

Differences in the brains of those with SAD

Researchers have identified several important differences in terms of the way that brains of people with SAD respond to stressful situations. These ground-breaking findings were achieved by using Functional Magnetic Resonance Imaging (fMRI) technology, which maps out neural activity in the brain.

The first major finding was that people with SAD are more likely to have an overactive amygdala. Recall that the amygdala is the primitive part of the brain that triggers the fear response if it senses danger. So, in social situations, the amygdalae belonging to people with SAD tend to be so jumpy that they shoot-off the fear response even for non-threatening stimuli. This is why, for example, you might be at a dinner party and find yourself in fight-or-flight mode for no apparent reason: the amygdala is responding to many stimuli, not only threatening ones! An angry or aggressive face might be a real sign of danger, but for people with SAD, something as benign as a cough, a raised eyebrow or a yawn may be enough to cause anxiety.

The second important difference is in the pre-frontal cortex. Recall that the PFC is the rational part of the brain that properly evaluates the situation and then helps to calm down the amygdala’s automatic fear response when there is no danger. In the brains of people with SAD, the research suggests that their PFC excites the action of the amygdala, rather than inhibiting it. Therefore, instead of doing the important job of calming down the jumpy amygdala the PFC actually galvanises it, triggering a fight-or-flight response even when this not necessary.

So where does this leave us?

Knowing what happens in the brain during an episode of social anxiety is helpful for several reasons. It helps those with SAD to understand more about what is happening in their minds and bodies when they experience a seemingly irrational bout of anxiety. These insights also may help reduce stigma by allowing us to reframe SAD and anxiety as, to some extent, an adaptive response that has helped humans survive since pre-historic times. Finally, a neurobiological perspective is important for developing treatments, such as CBT and neuropsychotherapy, both of which aim to bring about changes in specific neural pathways in the brain. In this way, knowing more about the brain has facilitated the development of therapies which actively attempt to manage SAD by re-wiring the brain patterns that are responsible for social anxiety.

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Sources:

Amaral, D. G. (2002). The primate amygdala and the neurobiology of social behavior: implications for understanding social anxiety. Biological psychiatry, 51(1), 11-17.

Mathew, S. J., Coplan, J. D., & Gorman, J. M. (2001). Neurobiological mechanisms of social anxiety disorder. American Journal of Psychiatry, 158(10), 1558-1567.

Phan, K. L., Fitzgerald, D. A., Nathan, P. J., & Tancer, M. E. (2006). Association between amygdala hyperactivity to harsh faces and severity of social anxiety in generalized social phobia. Biological psychiatry, 59(5), 424-429.

Sladky, R., Höflich, A., Küblböck, M., Kraus, C., Baldinger, P., Moser, E., ... & Windischberger, C. (2015). Disrupted effective connectivity between the amygdala and orbitofrontal cortex in social anxiety disorder during emotion discrimination revealed by dynamic causal modeling for fMRI. Cerebral Cortex, 25(4), 895-903.

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