Chapter 81

### Introduction

Anxiety is a thin stream of fear trickling through the mind. If encouraged, it cuts a channel into which all other thoughts are drained.

Arthur Somers Roche

Anxiety is a normal human physiological response that helps us respond to potential threats or dangers. We cannot get by without it. With an increase in anxiety, our performance should increase accordingly (e.g. preparing for exams). When we have too much anxiety, however, a further increase in anxiety will lead to our performance dropping off, described by the Yerkes–Dodson curve (see FIG. 81.1). The optimal place to be on the curve is to the left of the peak, so we have a positive response in our performance to an increase in stress. Being at the peak or to the right will make us vulnerable to stress.

###### FIGURE 81.1

Yerkes–Dodson curve

Anxiety becomes a problem when the stressor overwhelms us, resulting in poor performance, or if the unwanted consequences of the anxiety response give us undesirable physiological consequences. The stressor causes limbic activation, which in turn leads to autonomic and neuro-endocrine activity (down-regulation) that causes various physiological responses, including activation of the hypothalamic–pituitary axis. Blood flows from the gut to the skeletal muscles, there is activation of smooth muscle contraction in the bowels and an increase in nausea, muscle tension increases, the pupils dilate, the heart rate increases and blood pressure rises. The various somatic symptoms commonly seen in anxiety disorders can be explained by this (e.g. tension headaches, palpitations, eye strain and irritable bowel-like symptoms). In high stress situations, a flight–fright–freeze response can ensue.

The physiological role of anxiety and the way in which excess anxiety can cause these physical symptoms can be explained to patients suffering from anxiety disorders—and the GP is very well placed to conduct such psycho-education. Patients suffering from somatic symptoms are often unaware of the physiological consequences of anxiety and usually find this clarification comforting. It can help motivate patients to pursue strategies to reduce them.

### Prevalence and classification of anxiety

Anxiety disorders affect 14% of the population,1 with many people fulfilling the criteria for multiple anxiety disorders, also a common co-diagnosis of depression.2 Specific phobias are the most common anxiety-related diagnosis (1 in 5 women and 1 in 10 men), and PTSD is the most common disorder (over 6%).1 Anxiety disorders listed in the DSM-5 are:3

• separation anxiety disorder

• selective mutism

• specific phobia

• social anxiety disorder (social phobia)

• panic disorder

• panic attack (specifier)

• agoraphobia

• generalised anxiety disorder

• substance/medication-induced anxiety disorder

• anxiety due to another medical condition

• other specified anxiety disorder

• unspecified anxiety disorder

Other conditions discussed in this chapter include:

• obsessive–compulsive disorder

• body dysmorphic disorder (see CHAPTER 45)

• post-traumatic ...

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