Chapter 3
Investigating the Brain and Biology
IN THIS CHAPTER
Most people with anxiety describe uncomfortable physical symptoms that go along with their worries. They may experience heart palpitations, nausea, dizziness, sweats, or muscle tension. Those symptoms are evidence that anxiety is truly a disorder of both the mind and the body.
In this chapter, we review some of the biological roots of anxiety, as well as the consequences of chronic stress on health. Then we tell you about medications or food that can actually make you feel anxious. Finally, we discuss how some illnesses can cause or mimic anxiety.
Examining the Anxious Brain
The brain takes in information about the world through sight, taste, smell, sound, and touch. Constantly scanning the world for meaning, the brain integrates information from the past with the present and plans what actions to take. For most people, most of the time, the brain does a pretty good job. But for those with chronic anxiety, something goes awry.
Billions of nerve cells (neurons) reside in the brain. They’re organized into a variety of complex structures or circuits. Some of these structures are particularly involved in producing feelings of anxiety, fear, and stress. These brain structures communicate with one another by sending chemical messengers, known as neurotransmitters, back and forth among them.
In the following sections, we explain how the brain interprets information and what role the brain’s chemicals play in making you anxious.
How the brain’s circuits connect
Think of the brain as having many interconnected circuits. One circuit involves both the limbic system and the frontal lobes. To keep it simple, the limbic system is a primitive region of the brain and is responsible for immediate reflexive responses to threat. The thalamus and the amygdala form part of the limbic system. The frontal lobes, which handle judgment and reasoning, respond more slowly and thoughtfully.
When the brain perceives something as being dangerous, it immediately registers in the brain’s control center known as the thalamus. The thalamus rapidly sends a signal directly to the amygdala, which activates reflexive fear responses. Those responses prepare the body to fight or flee. The thalamus also delivers a warning signal through the frontal lobes. The frontal lobes, where rational thought occurs, take a little more time and use reason and logic to determine the veracity of the incoming threat. That’s why when you perceive something as being scary, your body immediately responds with a rapid heartbeat, tension, and dread. If and when the rational frontal lobes figure out that the scary thing actually doesn’t pose a significant threat, you calm down. That’s the way the brain is supposed to work.
For example, around the Fourth of July you hear loud popping sounds. Your limbic system may initially interpret those as gunshots, but your frontal lobes take a few seconds longer and conclude that the sounds are likely to be firecrackers. However, dogs, who don’t understand calendars or have well-developed frontal lobes, remain fearful.
In anxiety disorders, either the limbic system or the frontal lobes (or both) may fail to function properly. Thus, the limbic system may trigger fear responses too easily and too often, or the frontal lobes may fail to use logic to quell fears set off by the limbic system. When the brain signals danger, the body responds by getting ready for action. The next section explains the chemical aspects of fear.
Neurotransmitters
Neurotransmitters help nerve cells communicate feelings, fears, emotions, thoughts, and actions through an intricate orchestration. Four major neurotransmitter systems and some of their functions include
The noradrenergic system, which produces norepinephrine and epinephrine. It also stimulates organs required in the fight-or-flight response (see the following section).
The cholinergic system, which activates the noradrenergic neurotransmitters and facilitates formation of memories.
The dopaminergic system, which is involved in movement and is also related to feelings of pleasure and reward. Dopamine disruptions cause problems with attention, motivation, and alertness, and appear to be quite important in the development of fear responses.
The serotonergic system, which is related to moods, anxiety, and aggression.
STRESS AND VULNERABILITY TO INFECTION
A significant body of research spanning decades of work has linked stress and susceptibility to infections. This finding appears to be due to reductions in immune response and increased inflammation in highly stressed individuals. A recent study reported in the British Medical Journal looked at large groups of people with stress disorders, their siblings, and a group of people without stress disorders from the general population of Sweden.
After following the subjects for over 25 years, researchers found that people with stress disorders were significantly more prone to infections, including life-threatening infections. The study controlled for economic factors, family background, prior medical history, and a host of other variables.
The study may have implications for new viral infections as they inevitably arise. People with high levels of stress may be more susceptible to becoming infected as well as have a more difficult time recovering than those with lower stress levels. Furthermore, some research suggests that people with high levels of stress may not benefit as much as others from vaccinations. Thus, managing stress and anxiety may improve important health outcomes. These findings may ultimately prove to be especially important during times of pandemics.
As these neurotransmitters pulse through your brain, the brain circuitry involved in fear and anxiety lights up. Your body then responds with a full-system alert known as the fight-or-flight response.
Preparing to Fight or Flee
When danger presents itself, you reflexively prepare to stand and fight or run like you’ve never run before. Your body mobilizes for peril in complex and fantastic ways. Figure 3-1 gives you the picture.
© John Wiley and Sons
FIGURE 3-1: When presented with danger, your body prepares itself to flee or stand and fight.
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