Welcome to the very first post of our “A-Z” series, where we will give summaries of common themes, methods, or concepts that are often mentioned or discussed on the blog. Here, we start at the beginning (which is where things normally start) with the letter A, for Anxiety. Everybody feels anxious sometimes. We are all familiar with those moments when you can feel your heart start to race or you can’t stop worrying about your upcoming presentation. But when does anxiety become clinical and what are the different sub-types? This blog also outlines what we know about prevalence, onset patterns, heritability, and available treatments.



There is a difference between healthy, “normal” anxiety and a clinical diagnosis of an anxiety disorder. Anxiety is typically a temporary state that everyone experiences on a continuous spectrum of severity, from feeling slightly nervous to meet someone new to feeling panicked at the prospect of missing a flight.

Believe it or not, anxiety can even be helpful at times. The physiological arousal that we feel when we are anxious (that feeling of your heart beating faster and your palms starting to sweat) has evolved to help us confront stressful or anxiety-producing situations. In fact, one study found that simply instructing people to think of this anxious feeling as being functional and adaptive resulted in better performance at a cognitive task compared to controls.

However, anxiety can sometimes be experienced at an extreme level for extended periods of time, such that the experience of these emotions begins to impair everyday life and interpersonal relationships.

This is when anxiety can be classed as a clinical disorder. The Diagnostic and Statistical Manual, 5th edition (DSM-5) is the standard guide used to diagnose mental health disorders. According to the DSM-5, anxiety disorders “share features of excessive fear and anxiety and related behavioural disturbances.”

The key word here is excessive – in order for anxiety to be classed as a disorder, it must exceed what would generally be considered developmentally appropriate. Anxiety disorders are often persistent, typically lasting 6 months or more.

Types of Anxiety Disorders

Within the classification of an anxiety disorder, there is also a wide variation in symptoms that can be grouped into distinct diagnoses and sub-types. Below are details from the DSM-5 about a few of the more well-known anxiety disorders:

Generalised Anxiety Disorder (GAD) – Generalised anxiety disorder is what commonly comes to mind when someone speaks about clinical anxiety. The disorder is characterised by excessive worry that is difficult to control, and may relate to a variety of topics, including events or circumstances in the past, present, or future, that may or may not have occurred.

Panic Disorder – Panic disorder refers to recurrent, or more than one, panic attacks that have no obvious cue or trigger. Panic attacks are abrupt surges of intense fear or discomfort that are accompanied by various physical and cognitive symptoms, such as sweating, trembling, chest pain, numbness, or fear of dying. This disorder also involves persistent worry about having panic attacks and/or a change in behaviour to avoid having one again.

Agoraphobia – Agoraphobia is often known as being a fear of being in public situations, but generally people don’t realise that this fear comes from thoughts that escape might be difficult or help may not be available if something happens.

Social Anxiety Disorder (Social Phobia) – Social anxiety is the fear of negative assessment by others, which leads to anxiety about social situations or interactions. Oftentimes this leads to avoiding social situations so as not to be judged by others.

Specific Phobia or Fear – Phobias involve intense fear or anxiety about a specific object or situation, such as flying or heights. Similar to social phobia, the fear-inducing object or situation is typically avoided and causes significant distress, impacting the individual’s life.

Note: Although many of these anxiety disorders involve fear, there are some differences between anxiety and fear which will be discussed in a later blog post.

Lifetime Prevalence

Anxiety disorders are fairly common, impacting between 15-30% of people in Europe at some point in their life. Specific phobias are the most common of the anxiety disorders, with a lifetime prevalence of 8-13%, followed by generalised anxiety disorder (4-7%), panic disorder (2-5%), social anxiety disorder (3-13%), and agoraphobia (1-3%).

It can be difficult to measure the prevalence of a disorder because many people are undiagnosed, so these numbers are likely higher.

Age of Onset

The median (middle) age of onset for anxiety disorders is 11 years old, meaning that about half the people with an anxiety disorder will be diagnosed by the time they are 11. This is about 20 years earlier than depressive disorders. Specific phobias start the earliest with a median age of onset of 7 years, whereas generalised anxiety disorder (GAD) is the latest at 31 years.


Heritability is an estimate of the genetic influence on a trait or disorder – the extent that individual differences in the population are explained by genetic differences (expect more details about heritability when we reach the letter H!). The heritability of anxiety disorders is estimated to be around 30-40% across the lifespan. Obsessive-compulsive behaviours are estimated to have the highest twin-based heritability at around 45-60%, although generalised anxiety is also high at an estimated 32-40%. On the other hand, fears and phobias show more evidence of an environmental impact, which seems to make sense since fears generally arise due to bad experiences. The implications of anxiety being under genetic influence are hard to see at present, as little is known about the specific genetic variants involved. However, in time, it is likely we will be able to use genetic information to help personalise treatments. For example, we are doing work exploring the role of specific genetic factors in understanding outcomes following psychological treatment (more on this when we get to “T for therapygenetics”).


Alongside genetics, the environment also plays an important role in the development of anxiety and related disorders. One of the most well-known risk factors for anxiety, and indeed for many mental health difficulties, are stressful life events. People who have had a higher number of negative, unpleasant, or traumatic events occur throughout their lives are at a greater risk of developing anxiety disorders. Researchers in the ’80s found that severe loss was a causal factor in the onset of depression, whereas severe danger or threat was a causal  agent in the onset of anxiety. Bullying in childhood, for instance, is associated with higher rates of anxiety disorders for victims in adult life compared to non-victimised peers.

Available treatments

Some good news! There are evidence-based treatments available, which include medication as well as talking therapies. The most researched form of talking therapies is cognitive-behavioural therapy, or CBT (more information about CBT coming soon). In fact, the NHS suggests that individuals with anxiety start with self-help either by taking online courses or reading books based on CBT, attending support or peer groups, exercising regularly, and avoiding caffeine, alcohol, or drugs.

The NHS has also taken steps in the last decade to address the number of people in the UK with anxiety that were unable to access treatment. The Improving Access to Psychological Therapies (IAPT) initiative began in 2008 with the goal of providing evidence-based talking therapies to patients with anxiety and depression, based on the National Institute for Health and Care Excellence (NICE) guidelines. About 50% of people accepted onto IAPT services show improvement in their symptoms. Hopefully with more research aiming to better understand the causes of anxiety and how people may respond differently to certain types of treatment, this number will continue to increase.


This animation provides a useful overview of anxiety.


Thanks to Astrid Breitenstein for helping with background research for this blog post.



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Molly Davies

Author Molly Davies

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