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What is Anxiety? Exploring the Causes, Function, and Symptoms

Updated on April 22, 2016
Thomas Swan profile image

Dr. Thomas Swan has a PhD in psychology from the University of Otago.

Anxious is unpleasant for a reason.
Anxious is unpleasant for a reason. | Source

What is Anxiety?

Anxiety is an emotion that's best described as a prolonged feeling of uneasiness, apprehension or nervousness about potentially threatening events that haven't happened yet. It's triggered by objects, people, or modes of thought that suggest the emergence of a physical or social threat. Examples might include preparing for a public speech, hearing a tornado warning, or seeing a bear's footprint while hiking. These events each foretell an uncertain, unavoidable, or uncontrollable future threat.

Much like pain or fear, anxiety is an unpleasant warning system that tells us to avoid danger. However, unlike these other sensations, it activates well in advance of any real threat, utilizing the imagination and memory to simulate worst case scenarios. Anxiety also causes our cognitive capacities to change. For example, we'll start scanning the environment for further signs of danger, and interpret stimuli in threatening ways. Thus, anxiety’s fundamental function is to direct thought, behavior and cognition in ways that increase the likelihood of the early detection of danger.

Anxiety and Fear

Anxiety and fear are distinct emotions with different causes and effects. Anxiety is evoked by signs of potential danger, leading one to exhibit increased vigilance and precautionary behavior. Fear is produced when we are faced by an immediate, observable threat. It triggers an instinctive flee, fight, or freeze response.

State and Trait Anxiety

Most psychology textbooks separate the emotion into two parts. State anxiety simply refers to one's current anxious feelings. Trait anxiety is an affective personality trait, defined as relatively stable individual differences in anxiety proneness. About 30% of population variance in trait anxiety is described by genetic factors, with the remainder shaped in development.

Traumatic experiences can serve to increase trait anxiety during a person's life. These experiences form `danger schemas' in the brain, which are filled with memories, beliefs, and knowledge related to sources of the trauma. Anxiety resurfaces when stimuli are detected that relate to what is in the schema.

Anxiety disrupts attention and memory.
Anxiety disrupts attention and memory. | Source

Cognitive Effects of Anxiety

People who suffer from trait anxiety experience a number of cognitive biases that alter how they direct attention to, interpret, or recall threatening stimuli. These include:

  • Hyper-vigilance: A tendency to scan the environment for threats, leading to distraction from other tasks.
  • Interpretive bias: A proclivity to interpret ambiguous stimuli as threatening.
  • Specific hyper-vigilance: A narrowing of attention to focus on detected threats.
  • Negative memory bias: A propensity to remember and recall more threat-related than non-threatening information.

These biases are sometimes turned inwards. For example, they can cause people to view their own anxious state as worse than it is, amplifying anxiety further. Indeed, these biases are more severe in trait-anxious individuals who are already in an anxious state.

Cognitive scientists have revealed many of the effects that anxiety has on our ability to perform basic tasks. Their experiments show that task performance is hindered because anxiety generates irrelevant, threatening thoughts that reduce attention for the task at hand. Other experiments show that some anxious people perform adequately on tasks, but they have to expend greater effort than non-anxious people.

According to these researchers, anxiety disrupts attentional control by shifting attention to potential sources of threat. This motivation to `learn' about one's hostile environment is accompanied by reduced input from one's personal goals (such as completing a task) if those goals are unrelated to the source of anxiety. Instead, one's attention is divided across a medley of stimuli, picking out that which is salient based on primitive innate favoritism.

We are born with a repertoire of anxious triggers; such as wild animals!
We are born with a repertoire of anxious triggers; such as wild animals! | Source

The Evolution of Anxiety

Anxiety would have been absent in humans before the evolution of episodic memory. This trait describes our ability to mentally travel in time, allowing us to scrutinize knowledge for accuracy and reliability, and creatively combine events to explain the present or anticipate the future. It is a recently evolved capacity associated with the prefrontal cortices. Episodic memory allows one to anticipate future sources of fear, which is essentially what anxiety is.

Many of the triggers and solutions for anxiety have been ingrained in our minds by evolution. For example, pregnant women display an adverse reaction to foods with high contamination risk (e.g. meat). Conversely, when males see a potential for status loss, they become disposed towards building alliances and coalitions. We have evolved to detect and combat these sources of anxiety because they were prevalent in our ancestral environment. In general, we are highly attuned to sources of inter-species violence, predation by animals, contamination, and social status loss. These basic, evolved anxieties are culturally augmented as we grow older. For example, we have an innate fear of predators, and children often imagine monsters with distinct predator features (claws and fangs). However, only experience can identify culturally relevant predators (such as tigers in India).

To detect these sources of anxiety, we have what's called an appraisal system. If a stimulus is evaluated (appraised) in the following ways, anxiety may be generated:

  • The stimulus is relevant to my goals, but could be in opposition to them.
  • My ability to cope is low or uncertain. (An inability to cope causes stress).
  • There is no obvious object of blame. (Blame would cause anger).
  • The outcome is uncertain or beyond my control.

The resultant anxiety is felt as an unpleasant emotion that motivates one to undertake precautionary action. Usually, this action cannot confirm the threat’s removal, meaning the anxiety could linger indefinitely. However, much like a child checking a room for monsters, a flawless, ritualized, performance of precautionary behavior can work to reduce anxiety. As an added benefit, the vigilance characterizing anxiety causes us to learn about our environment in order to increase the effectiveness of precautionary routines (such as checking every nook and cranny for monsters!).

An Ever-Present Emotion

The Danish philosopher, Søren Kierkegaard, reasoned that anxiety commonly arises from our persistent fear of death, non-existence, non-being, or nothingness. Indeed, if we are to survive in a dangerous world, it must be adaptive to be regularly reminded of what the ultimate consequence is! Other sources of anxiety such as loneliness, poor health, social ostracism, money, and relationship troubles are temporary in comparison, but all impinge on our ability to survive.

As death is an inescapable inevitability, no precautionary behavior can completely remove this existential anxiety. However, in futile attempts to overcome it, beliefs that deviate from normal reality may become more attractive. For example, most religions include some form of afterlife, raising the possibility that religious belief might serve to reduce existential anxiety. Indeed, religious rituals are commonly used to suppress other anxieties. Pascal Boyer has shown that rituals use repetition, rigidity and goal demotion to reduce anxiety by swamping our working memory. Incidentally, this is also why OCD sufferers exhibit ritualized behavior.

As well as these extreme cases of ritual behavior, most people have rituals that serve to demonstrate control over their environment. It could be something as simple as double checking the stove is off, placing the TV remote in a particular place, checking a child's room for monsters, or ensuring that one's coat-hangers all face the same way. This ritualized display of control serves to reduce anxiety.

The idea that anxiety is a constant fixture in our lives is supported by experiment. For example, Angela Byrne found that highly anxious people took longer to notice a happy face in a crowd of angry faces. This is expected because anxious people are distracted by threatening stimuli. However, they also found that all participants took longer to notice a happy face in a crowd of angry faces, compared with an angry face in a crowd of happy faces. This suggests that we have an ever-present, base-line level of anxiety.

People who repress their anxiety may be more willing to fight in wars.
People who repress their anxiety may be more willing to fight in wars. | Source

Anxiety Defense Mechanisms

Some people with trait anxiety problems will unconsciously repress it in order to cope with it. These repressors score high on social desirability questionnaires, which measure defensive coping styles for the protection of self-esteem. Repressors display cognitive biases that are the opposite of what normal people with trait anxiety display. Thus, repressors will ignore threatening information, or reinterpret it optimistically.

As a result, repressors can sometimes ignore threats to their peril. However, repression may be an adaptive strategy for minimizing the unpleasant experience of persistent anxiety. Furthermore, the cultural norms of most societies favor individuals who display less anxiety. Ultimately one’s developmental environment will determine if repression is adaptive, and which threatening stimuli are ignored. For example, some repressors have been shown to ignore social threats, but not physical threats.

Measures of Anxiety

Anxiety correlates with:

  • Increased heart rate.
  • High blood pressure.
  • High cortisol (stress hormone).
  • Increased sweating.
  • Muscle tension.
  • High skin conductance response.
  • Autonomic nervous system reactivity.
  • Pupil dilation.
  • Behavioral inhibition.

The Physiology of Anxiety

The amygdala, which is associated with motor activity and distress calls in animals, appears to govern human physiological responses to anxiety (see right). In addition to the obvious signs of distress, high anxiety is correlated with the increase of a chemical called neuropsin, which is important for learning and memory. As anxious individuals show a disposition to scan the environment for threats, neuropsin helps the individual to assimilate this data.

Furthermore, experiments showed that levels of fibroblast growth factor 2 increased after anxious episodes. FGF2 increases the survival rate of new brain cells in the hippocampus. Again, this demonstrates the role anxiety plays in assimilating new information from the environment.


Anxiety is probably the most important emotion in our affective repertoire. Like fear, it functions to warn of impending danger; but unlike fear, it remains with us as a constant reminder of the threats we are likely to face. Like all products of evolution, anxiety isn't a perfect construct. Those with high trait anxiety are tormented by unpleasant feelings that distort the way they view the world. This species-wide variance in our proneness to anxiety could potentially act as a buffer against a deteriorating environment. Indeed, anxiety helps individuals to learn about threats in their environment, and motivates behavior that may prove vital during times of adversity.

© 2013 Thomas Swan


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