Nearly everyone experiences moderate anxiety at some point in their lifetime, and most of us feel anxiety, at least in small degrees, nearly every day (hesitancy to approach a stranger due to fear of rejection, worries about money, concerns about what others think, etc.).

By definition, anxiety is a feeling of apprehension, uneasiness, uncertainty, or dread resulting from a real or perceived threat.

Anxiety is a universal human experience and is among the most basic of emotions. Thus it is unavoidable in life and can serve many positive functions such as motivating the person to take action to solve a problem or to solve a crisis. It is considered normal when it is appropriate to the situation and dissipates when the situation has been resolved.

Anxiety is experienced at multiple levels. Subjectively, it is a largely negative emotion. Behaviorally, it often manifests as avoidance; the anxious individual may become relatively socially withdrawn or otherwise timid.

Physiologically, it involves activation of the sympathetic nervous systemOpens in new window, which produces the stress response. Physiological symptoms include increased heart rate, blood pressure, and respiration, release of stress hormones, and others. Chronic anxiety can also bring fatigue, difficulty sleeping, muscle tension, and irritability.

Anxiety vs Fear: Their Distinctiveness

AnxietyOpens in new window is a reaction to a perceived threat, as is fearOpens in new window. Unlike fear, however, which is a reaction to a specific stimulus or event, anxiety is often more diffuse or of uncertain origin. In other words, fear is a reaction to a specific danger, whereas anxiety is a vague sense of dread related to an unspecified or unknown danger. However, the body reacts physiologically in similar ways to both anxiety and fear.

In general, compared to fearOpens in new window, which occurs immediately after an event has transpired, anxiety is centered on a possible experience in the future. In terms of brain structures, anxiety appears to be related to activity of a part of the stria terminalsOpens in new window.

As Davis and his colleagues describe, the bed nucleus of the stria terminalis receives sensory input from a part of the brain (the thalamus) and, through connections with other anatomical structures (i.e., the hypothalamus of the brain and the brain stem), initiates long-lasting sympathetic nervous system responses (increased heart rate, etc.) in reaction to relatively vague threatening contexts. This action is different from, but overlaps with, the reaction that occurs with fear.

In fear, the thalamusOpens in new window sends information to part of the amygdale, which, like the stria terminals, has connections with anatomical structures that initiate sympathetic nervous system activity.

Through this circuit, a reaction is produced to specific threatening stimuli (loud noise, bear approaching, etc.); the fear response is similar to anxiety (increased heart rate, blood pressure, etc.) but tends to be more intense and of shorter duration.

Particular brain chemicals are implicated in anxiety. The chemical that has been most studied is the neurotransmitter gamma-aminobutyric acid (GABA)Opens in new window. GABA is the main brain chemical that inhibits the activity of neurons (i.e., when GABA interacts with a neuron, the result is that the usual activity of that neuron, i.e., firing, is decreased).

Substances that increase the activity and effectiveness of GABA tend to decrease anxiety. The earliest substances that were discovered to have this effect were tranquilizers such as diazepam (Valium)Opens in new window and chlordiazepoxide (Librium)Opens in new window. Thus tranquilizers are regularly used to treat anxiety conditions.

Unfortunately, these medications tend to have a host of side effects, partly because GABA inhibits activity of many types of neurons, not just neurons involved in the occurrence of anxiety. GABA suppresses activity in much of the brain, producing memory loss, sleepiness, and slurred movement and speech.

Anxiety or fearOpens in new window are present in the anxiety disorders that are described by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR; American Psychiatric Association, 2000)Opens in new window. The prominent feature of both generalized anxiety disorderOpens in new window and panic disorderOpens in new window is anxiety.

The reaction is simple phobias (fears of specific objects or situations such as dogs, snakes, blood, closed spaces, etc.), however, is more accurately described as fear. Other major anxiety disorders, social phobiasOpens in new window and posttraumatic stress disorderOpens in new window, involve both anxiety and fear. As researchers have learned more about anxiety and fear and the differences between the two, treatments for the various anxiety disorders have improved.