Anxiety Disorders

Todd A Smitherman. 21st Century Psychology: A Reference Handbook. Editor: Stephen F Davis & William Buskist. Volume 2. Thousand Oaks, CA: Sage Publications, 2008.

Anxiety disorders are highly prevalent in the general population and result in considerable suffering for millions of individuals. Consequently, much research has been conducted on the etiology, assessment, and treatment of anxiety disorders. Advances made within the field of anxiety disorders represent one of the great success stories within psychology over the last century. These advances demonstrate how empirical research and well-grounded theories can be used to inform clinical practice. For these reasons, anxiety disorders are of particular interest to students of psychology, especially those considering a career in clinical psychology.


Historical Overview

Although anxiety disorders were not officially recognized by the American Psychiatric Association until 1980, anxiety and fear have always played prominent roles in human history.

Civilizations have used chemical and herbal remedies to reduce fear and decrease pain for literally thousands of years. The ancient Greeks described citizens who were so fearful that they refused to leave their homes, a precursor to our modern concept of agoraphobia. Over the following centuries, civilizations attributed anxiety symptoms to the results of human sin or witchcraft, the work of evil spirits, or relatively crude assumptions about human biology.

Beginning in the late 1800s, and coinciding with the spread of psychology to America, fear and anxiety began to receive closer attention within the academic community. Charles Darwin, who himself experienced extreme panic attacks and agoraphobia, observed that lower animals were capable of panic-like symptoms and would “play dead” when threatened. Darwin’s evolutionary theory suggested that fear was an adaptive behavior, conferring a survival advantage by facilitating escape from and avoidance of danger. Years later, Freud described “neurotic anxiety” as the result of psychic conflicts and a reemergence of infantile fears related to sexual and aggressive impulses.

Conceptualizations of the anxiety construct began to change around the 1930s. Freudian psychoanalytic theory began to garner heavy criticism from more empirically minded psychologists because it was not testable, was based on case reports from a select group of patients, and overemphasized sexual and unconscious conflicts. Behaviorism gradually appeared in its stead, emphasizing the importance of studying observable behaviors and developing an evidence-based science of psychology. Several important events strengthened the behaviorist movement. The first event was the repeated demonstration that fear responses could be classically conditioned in animals, providing empirical evidence that fear obeyed common learning principles. The second event was the return to America of numerous World War II soldiers suffering from “shell shock,” similar to the current concept of post-traumatic stress disorder (PTSD). The seemingly direct relationship between these symptoms and combat exposure provided anecdotal support for the role of classical conditioning in human fear. The third event was the subsequent introduction of behavior therapy, which showed that classically conditioned fears could be reduced with various procedures arranging for safe and prolonged exposure to feared stimuli. The success of behavior therapy was taken as evidence for the role of conditioning in fear development and maintenance. These events legitimized interest in behavioral accounts of anxiety disorders and their treatment.

Although current conceptualizations of anxiety bear many similarities to those that were heavily influenced by behaviorism, realizations that conditioning accounts of anxiety were oversimplified and did not accord completely with the major empirical facts soon arose. The most prominent example is the two-factor theory of fear mediation (typically attributed to O. H. Mowrer), the prevailing theory of fear conditioning during the mid 1900s. According to two-factor theory, fear is originally learned through classical conditioning but is later maintained by operant conditioning in the form of avoidance behavior. Avoidance prevents the individual from learning that there is no longer anything to fear, but it is negatively reinforced (and thus persists) because it reduces anxiety. Criticisms of Mowrer’s theory focused on both the classical conditioning and operant conditioning components. Classical conditioning alone could not explain the origins of all fear development, as numerous studies showed that many phobic individuals could not identify a specific conditioning event that initiated their fear. These findings led researchers such as S. J. Rachman and Albert Bandura to suggest that fears could be learned also through watching others behave fearfully (i.e., modeling, observational learning) or by being told that certain stimuli should be feared (i.e., information transfer). Criticisms of the role of operant conditioning in maintaining fear centered primarily on the failure to demonstrate consistently the predicted relationship between avoidance and fear in various experimental settings. As detailed in reviews by Delprato and McGlynn (1984) and Rachman (1976), studies accumulated showing that fear often persists even when avoidance has been eliminated, that many individuals will approach a feared stimulus despite reporting extreme fear, and that minimal fear is evidenced when the avoidance response becomes habitual. Although Mowrer’s theory is still a useful heuristic for discussing the influences of conditioning on fear, the criticisms above underscore the fact that strict conditioning accounts neglect other factors involved in fear development and maintenance.

Inadequacies in purely behavioral accounts of anxiety prompted psychologists in the latter half of the 20th century to focus instead on cognitive and information-processing aspects of anxiety. These cognitive theories highlighted the importance of maladaptive thinking patterns (including catastrophic expectations about experiences with feared stimuli) and biased processing of threat-related information as factors that maintain anxiety. The work of Aaron Beck emphasized the central role of core beliefs related to perceived danger and vulnerability, and others such as Albert Ellis and Donald Meichenbaum described the importance of modifying maladaptive cognitions in their unique forms of cognitive therapy.

Corresponding with these developments in the cognitive arena were advances in technology that afforded more accurate understanding of the physiological and biological influences on anxiety and fear. Physiological influences involve those associated with the autonomic nervous system. More recent neurobiological advances include identification of relevant neurotransmitters, brain structures, and pathways between brain structures and stress hormones (described in more detail later). Most recently, behavioral, cognitive, and biological elements have been integrated into more complex models.

Current Conceptualizations of Anxiety Disorders

Anxiety as a Three-Channel System

The cumulative effect of these historical developments was the realization that anxiety and fear are extremely complex emotions. Peter Lang (1968) articulated this fact by describing anxiety as a “three-channel” system with subjective, behavioral, and physiological aspects. Subjective elements include thoughts, beliefs, assumptions, and the like that are self-reported. Behavioral components include observable signs of anxiety such as approach/avoidance behaviors and overt signs of discomfort (e.g., gestures, facial expressions). Physiological determinants are those controlled primarily by the sympathetic nervous system, such as increased heart rate, respiration, and blood pressure.

According to Lang, the subjective, behavioral, and physiological components of anxiety are relatively independent of one another. Within any individual, contributions of the three components may differ at any point in time (discordance) or change at different rates over time (desynchrony). For example, a person with an extreme fear of public speaking may think during the speech that he or she is not communicating clearly (subjective) and evidence increased heart rate (physiological), but may display no visible signs of anxiety to audience members (behavioral). As the speech progresses, heart rate may decrease even though anxious cognitions remain. However, for another individual, the constellation of subjective, behavioral, and physiological factors may be entirely different.

Lang’s account of anxiety as a three-channel system is more of a descriptive model than an etiological one, highlighting the fact that anxiety manifests in different ways among different individuals and at different points in time. Though it does not present a thorough account of how anxiety develops or is maintained, the three-channel view has provided clinicians and researchers with a useful framework for understanding how anxiety is experienced. The continued impact of Lang’s model is evident in contemporary methods of anxiety assessment, as described later.

Multidimensional Models

Efforts are now being made to integrate the cognitive, behavioral, and physiological/biological aspects of anxiety into larger, multidimensional models that explain how anxiety disorders develop and are maintained. David Barlow’s (2000, 2002) model of panic disorder is the best exemplar. According to Barlow, some individuals are particularly vulnerable to developing an anxiety disorder. A person may inherit a general biological vulnerability toward anxiety and develop psychological vulnerabilities based on early life experiences with uncontrollable situations. These preexisting vulnerabilities, when combined with stressful life situations, may produce unusual bodily sensations. Because the bodily sensations are experienced simultaneously with fear (in the initial form of a panic attack), they become cues for fearful thinking anytime they are noticed. The individual begins to focus excessively on any unusual bodily sensations because he or she is now fearful of the sensations and believes they are dangerous. The increased attention to bodily sensations increases fearful thinking and ultimately leads to avoidance of situations wherein the feared sensations may occur. The cycle repeats and continues, with fearful thinking occasioning panic symptoms and vice versa.

Barlow’s multidimensional models of the other anxiety disorders are similar, with some disorder-specific variations. These models denote the contribution of inherited and learned vulnerabilities in conjunction with life stress; if either of these conditions is lacking (preexisting vulnerability or significant life stress), an anxiety disorder will not develop. These models also emphasize the role of anxious thinking and avoidance in maintaining anxiety and fear. Although much work remains in refining such complex models, they serve to organize thinking about how anxiety disorders are shaped by both biological/psychological diatheses and particular life experiences.

Distinctions among Anxiety, Fear, and Panic

Although the terms “fear,” “panic,” and “anxiety” are often used interchangeably, current thinking is that these terms denote different concepts. Historically, the prevailing view was that the presence of an identifiable fear cue differentiated fear from anxiety: Fear was triggered directly by a specific stimulus (e.g., snake, crowded place), while anxiety was more diffuse and was experienced in the absence of a specific fear stimulus. More recently, theorists have emphasized that panic and fear are relatively similar emotional states; both function to promote escape upon exposure to immediate danger (similar to the “fight-or-flight” response). Panic typically refers to a more intense experience than fear, and an individual experiencing a panic attack may have difficulty identifying the stimulus that provoked the attack. Likewise, many people experience fear but do not experience panic attacks. Anxiety, in comparison to panic and fear, usually refers to a more generalized and future-oriented emotion (entailing worry, apprehension, and planning). Anxiety serves to prepare an organism to detect, appraise, and cope with potential threats and is often expressed through hypervigilance, scanning the environment, and appraising coping strategies. Because conditions with prominent panic and fear components are also labeled as “anxiety disorders,” the distinctions among fear, panic, and anxiety are still often blurred.

Methods: Diagnosis and Assessment

The Major Anxiety Disorders

Generally, most anxiety disorders are characterized by intense fear or anxiety about certain stimuli and some type of avoidance behavior(s). The fear and avoidance must interfere with the individual’s functioning or be extremely distressing; otherwise, the individual may be fearful but does not merit a diagnosis. The criteria required for diagnosis of each anxiety disorder are outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR; American Psychiatric Association, 2000), which provides a useful but inexact grouping of all psychological disorders based on their presenting symptoms. One result of this grouping system is comorbidity, a term that refers to the fact that many individuals meet diagnostic criteria for more than one disorder. Anxiety disorders are most frequently comorbid with other anxiety disorders, depression, and substance use disorders. Because DSM-IV-TRdescribes the key features of each anxiety disorder in considerable detail, a brief overview of that information is provided here.

Panic Disorder

A panic attack is defined as a sudden period of biological and/or cognitive fearfulness that typically peaks within 10 minutes and then subsides gradually. Symptoms experienced during panic attacks include rapid heart rate, shortness of breath, sweating, feeling dizzy or lightheaded, fears of dying, and fears of losing control or going crazy, to name several. Panic disorder (PD), in turn, is characterized by (a) recurrent, unexpected panic attacks (that appear to come “out of the blue”) as well as (b) persistent concern about having another attack, worry about the implications of the attacks or their consequences, or significant changes in behavior related to the attacks. Often, significant changes in behavior manifest as agoraphobia (panic disorder with agoraphobia), in which the individual avoids many situations in which a panic attack may occur or in which help may not be available in the event of panic (e.g., shopping malls, grocery stores, and other places outside the home). One central feature of PD is anxiety sensitivity (Reiss, Peterson, Gursky, & McNally, 1986), which denotes the belief that bodily sensations of anxiety are dangerous due to their presumed negative consequences (e.g., the belief that an increase in one’s heart rate is dangerous because it signals an impending heart attack). Indeed, a focus on catastrophic misinterpretations of relatively benign bodily sensations is central to cognitive models of panic disorder (see Clark, 1986).

The lifetime prevalence rate of PD (with or without agoraphobia) is between 1.5 percent and 3.5 percent, meaning that between 1.5 percent and 3.5 percent of the population will meet criteria for PD at some point in their lives. Onset of PD typically occurs between late adolescence and the mid-30s. Like most other anxiety disorders, PD is more common in women than in men. Because strong bodily sensations are associated with panic attacks, individuals with PD frequently present to their primary care physician rather than to a mental health provider. A comprehensive physical evaluation is often warranted, in order to rule out serious medical conditions that may mimic panic attacks (such as chronic respiratory diseases, cardiovascular disease, epilepsy, etc.).

Social Phobia

Often referred to as social anxiety disorder, social phobia involves an intense fear of social or performance situations. Most typically, the individual fears being judged negatively by others, by either doing something embarrassing or having others notice that he or she is extremely anxious. Some individuals may experience panic attacks when exposed to social situations; however, in contrast to PD, the panic attacks are limited entirely to social or performance situations and are not experienced as unexpected or uncued. Feared situations often include public speaking, eating in front of others, using public restrooms, meeting new people, and going to parties. If the fear extends to most social situations, a diagnosis of social phobia, generalized subtype, is appropriate. Other features often associated with socially phobic individuals include being overly sensitive to criticism or rejection, social skills deficits (e.g., difficulty maintaining eye contact, problems being assertive), limited social support networks, and heightened levels of perfectionism.

Social phobia is recognized as a very common anxiety disorder, with lifetime prevalence rates typically ranging from 3 to 13 percent. A substantially higher percentage of individuals report excessive fear of public speaking, but most of these cases do not merit a diagnosis of social phobia. Onset of social phobia typically occurs in the teenage years, often among individuals who were very shy as children. Although onset of social phobia after age 30 is uncommon, many preteen children are diagnosed with social phobia after problems interacting with peers, teachers, or strangers are observed. Epidemiological studies indicate that social phobia is more common in women than in men, but half or more of those who present for treatment are male.

Specific Phobias

Another type of phobic disorder is a specific phobia, which refers to a persistent and excessive fear of a specific object or situation. Similar to social phobia, the feared stimulus is usually avoided and panic attacks, if they occur, are directly in response to the feared stimulus only. Five major subtypes have been identified: (a) animal type, if the fear is initiated by exposure to animals or insects; (b) natural environment type, for fear that is prompted by objects in nature, such as heights, storms, or water; (c) blood-injection-injury (BII) type, for fear that is cued by invasive medical procedures, by receiving an injection, or by seeing blood or an injury; (d) situational type, for fear that is prompted by a specific situation, such as enclosed spaces, public transportation, driving, or bridges; and (e) other type, for fear that is cued by an object not classified within one of the above categories, such as a fear of vomiting or of clowns. The situational subtype is observed most frequently.

Lifetime prevalence rates for specific phobias typically range from 10 to 11 percent. Despite the fact that virtually all specific phobias are more common in women than men, recent research has underscored the fact that the specific phobia subtypes differ in many other ways. For example, the onset of situational phobias is typically later than the onset of the other phobia subtypes, which usually emerge during childhood or early adolescence. As another example, BII phobics typically manifest a physiological response pattern opposite to that of other phobias. Instead of rapid and prolonged heart rate acceleration, BII phobia is characterized by a brief acceleration of heart rate, followed by a quick deceleration of heart rate and a decrease in blood pressure. As a result, and unlike other phobias, fainting is often observed in BII phobia upon exposure to the feared stimulus. Individuals rarely present for treatment for a specific phobia because they simply avoid the object they fear. Treatment is usually sought only if the individual will be unable to avoid the feared object (e.g., a businessperson with a flying phobia who has to give a presentation overseas) or because of comorbid conditions that merit treatment (e.g., PD, which is particularly comorbid with specific phobias).

Obsessive-Compulsive Disorder

The main features of obsessive-compulsive disorder (OCD) are recurrent obsessions and/or compulsions that are extremely time consuming, cause marked distress, or impair the individual’s functioning. Obsessions refer to intrusive and persistent thoughts, impulses, or images that are not simply exaggerated worries about real-life problems. Common obsessional themes include contamination/ disease, ordering/symmetry, doubting one’s safety or memory, harming someone, and performing inappropriate/unacceptable behaviors. For example, contamination obsessions typically involve extreme fear of contracting germs or diseases after touching certain objects; harming obsessions may include the sudden urge to throw hot coffee on a stranger, an impulse to run one’s car into a tree, or the mental image of a family member being killed; obsessions related to performing inappropriate behaviors may include thoughts of violent sexual acts, the sudden urge to swear in church, or having a thought contrary to one’s religious beliefs.

Compulsions refer to the repetitive and ritualistic behaviors that the individual feels compelled to perform in response to the obsessions and in order to prevent some feared event from occurring. In this regard, compulsions are similar to most avoidance behaviors. Compulsions may be overt behaviors or covert mental acts (e.g., praying, repeating words silently). Individuals with contamination obsessions wash their hands, shower, and clean excessively to avoid contracting diseases. People with obsessions about ordering or doubting may arrange insignificant items into precise positions, repeat certain behaviors a particular number of times, or repeatedly check certain objects (e.g., checking the door locks, checking to make sure the stove is off). Other common compulsions include repeating certain words silently, counting, praying excessively, and repeatedly requesting reassurance from others. Some compulsive behaviors may be driven by thought-action fusion, or the belief that negative thoughts and negative behaviors are morally equivalent (i.e., “thinking it is as bad as doing it”). Individuals high in thought-action fusion also believe that having a thought about a negative event makes it more likely that the event will actually occur (e.g., “Because I had the thought that my wife would die in a car wreck today, she is more likely to do so”).

Obsessive-compulsive disorder has a lifetime prevalence of 2 to 3 percent. Although less prevalent than social or specific phobias, OCD is one of the most disabling and time-consuming anxiety disorders, and entire inpatient hospital units have been developed for those with severe OCD. OCD usually has its onset in late adolescence through the early 20s, although childhood onset is not uncommon, especially in boys. Unlike most other anxiety disorders, the prevalence of OCD is relatively similar in males and females, with evidence suggesting that childhood OCD is more common in boys and that adult OCD is slightly more common in women. Care must be taken to distinguish the obsessions of OCD from the delusions of schizophrenia. Contrary to patients with schizophrenia and other psychotic disorders, patients diagnosed with OCD are usually able to recognize that their obsessions and compulsions are excessive, unreasonable, and a product of their own minds (ego-dystonic).

Post-Traumatic Stress Disorder

PTSD develops in a minority of individuals who experience an extremely traumatic and fear-provoking event, typically of a life-threatening nature. Other features required for diagnosis include repeatedly reexperiencing the trauma “as if it were happening all over again” (e.g., through nightmares, flashbacks, or intrusive memories), persistent efforts to avoid stimuli associated with the trauma and emotional numbing (e.g., reduced interest in certain activities, feeling detached from others, limited range of emotions), and symptoms of increased arousal that develop after the trauma (e.g., difficulty sleeping or concentrating, hypervigilance, angry outbursts, being easily startled). These criteria underscore the fact that PTSD is a very complex disorder and manifests differently in different individuals. Traumatic events include those in which the survivor directly experienced, witnessed, or learned about a life-threatening event or an event that threatened someone’s physical integrity. Common traumatic events include military combat; natural disasters; severe automobile accidents; being taken hostage or tortured; and being raped, kidnapped, or the victim of another serious crime.

Groups at higher than average risk of developing PTSD include soldiers who are in combat, emergency personnel (paramedics, firefighters, and police), individuals who were sexually abused as children, and members of communities who have experienced ongoing civil war or a natural disaster. Most individuals who experience a traumatic event, however, do not go on to develop symptoms of PTSD, contrary to some popularly held beliefs. Multiple studies have shown that between 40 to 60 percent of the general population has experienced or witnessed a traumatic event, although only 5 to 10 percent will meet criteria for PTSD at some point in their lives. There appears to be a dose-response relationship in the development of PTSD: Individuals who experience a more severe trauma, for longer duration, and within close proximity are most likely to develop PTSD. For example, a soldier who is held prisoner and tortured for three months is more likely to develop PTSD than someone who witnesses a bad traffic accident on the highway. Symptoms of PTSD can develop at any age, including childhood, and often occur within three months of the traumatic event. Epidemiological studies have shown that the rate of PTSD in women is about twice that in men.

Generalized Anxiety Disorder

Unlike the other anxiety disorders, in which discrete periods of fear or panic are relatively salient, generalized anxiety disorder (GAD) is characterized by more diffuse anxiety and worry (see the section above on differentiating fear and panic from anxiety). The core feature of GAD is chronic and excessive worry about a number of events and activities. The individual finds it extremely difficult to control the worry and typically experiences physical symptoms as a result, including restlessness, fatigue, difficulty concentrating or sleeping, muscle tension, and irritability/agitation. Worry that occurs in the context of other anxiety disorders is typically confined to the other disorder (e.g., worry about having an unexpected panic attack in PD, worry about performing inadequately during a speech in social phobia). The worry that characterizes GAD, on the other hand, typically relates to areas associated with everyday life, such as finances, employment, health, and school, as well as other minor matters and daily hassles. The broad focus of worry about real-life problems also serves to differentiate GAD from the obsessional thinking that characterizes OCD.

Individuals diagnosed with GAD are often described as “worrywarts” and frequently report that they have felt anxious throughout their entire lives. They are often unable to tolerate uncertainty; they worry excessively because they believe that doing so will provide them with more certainty about future events and their ability to handle them. For example, many GAD patients believe that their worry serves a useful function, such as preventing dreaded events from occurring, helping them prepare for the future, and enhancing coping skills (Borkovec, Hazlett-Stevens, & Diaz, 1999). However, studies investigating these beliefs have found inconsistent support for their accuracy. There is no strong and consistent evidence that excessive worry improves problem-solving or coping skills. On the contrary, worry appears to function much like an avoidance behavior; excessive worry has been linked to avoidance of emotions and interferes with active coping. Chronic worry also often involves negative events with low base rates (those that are unlikely to occur in the first place), creating the illusion that worrying prevented the dreaded events from happening.

Lifetime prevalence estimates of GAD are around 5 percent. Like PD patients, GAD patients often present in primary care settings and utilize health-care resources at a high rate. Onset of GAD is extremely varied. Many individuals report that their symptoms began in childhood, others report onset in adolescence or young adulthood, and a sizeable minority report onset after age 40. The course of GAD is often chronic, explaining why many older adults display symptoms of GAD. Symptoms are often worse during periods of extreme stress, as is true of other anxiety disorders. GAD is more prevalent among women than among men.


Comprehensive assessment provides the cornerstone for designing an effective treatment plan. Lang’s view of anxiety as a three-channel system provides a framework for the assessment of anxiety disorders. Assessment occurs at the levels of self-report, behavior, and physiology.

Assessment by self-report focuses on aspects of anxiety that are subjectively experienced and thus can be obtained only from the individual’s verbal or written report. Although many psychologists have expressed reservations about the reliability and validity of assessment data gathered from self-reporting, it remains the most common means of assessing anxiety (Lawyer & Smitherman, 2004). Methods for obtaining self-report data include clinical interviews, questionnaires, self-monitoring, and situational ratings. Clinical interviews are often structured so as to inform diagnostic decisions and obtain detailed information about anxiety-related problems, the most detailed being theAnxiety Disorders Interview Schedule for DSM-IV (ADIS-IV; Di Nardo, Brown, & Barlow, 1994). The ADIS-IV and similar interviews are often used in research studies to establish which participants meet diagnostic criteria for particular disorders. Questionnaires are easier to administer and score than interviews, and they provide a useful means of comparing the frequency and severity of an individual’s symptoms to those of others. Several important constructs highlighted earlier are assessed using questionnaires: anxiety sensitivity in PD patients, thought-action fusion in OCD patients, and intolerance of uncertainty in GAD patients. Many of the most commonly used questionnaires are reviewed and reprinted in Antony, Orsillo, and Roemer’s (2001) excellent sourcebook. Self-monitoring strategies involve having the anxious patient monitor and record particular behaviors or thoughts, similar to keeping a diary. The occurrence of panic attacks, avoidance behaviors, obsessions and compulsions, and instances of irrational thinking are common targets of self-monitoring. Finally, fear ratings typically are obtained in the context of exposure to a feared stimulus. Ratings may be obtained upon direct exposure to the stimulus (in vivo exposure) or while having the patient imagine the stimulus (imaginal exposure). Taken together, self-report methods provide useful but inexact data on how a given individual experiences and interprets his or her anxiety or fear.

Behavioral methods of assessment are more objective than self-report methods. They focus on behavior that is directly observable and are presumably less prone to error and distortion than self-report methods. Behavioral methods of anxiety assessment include behavioral avoidance tests, role-play exercises, and challenge tests. Behavioral avoidance tests afford the observation and measurement of behavior in the presence of a feared stimulus. They may occur in laboratory or natural environment settings and are used frequently in the assessment of social and specific phobias (e.g., observing a spider phobic’s behavior while approaching a live tarantula and recording how close he/she comes to the spider). Role-play exercises typically involve having socially phobic individuals interact in a contrived social situation (e.g., at a job interview, delivering a speech, asking out a date). Challenge tests, often used with PD patients, are designed intentionally to produce symptoms of panic and allow for observation of the individual’s response. Inhalation of carbon dioxide-enriched air, hyperventilation, and other exercises are often used to accomplish this goal. These behavioral methods are often used in conjunction with obtaining situational fear ratings or other self-reports of fear.

Physiological assessment refers to real-time monitoring of the autonomic nervous system, most typically that associated with output of the sympathetic nervous system. Commonly monitored processes include heart rate, blood pressure, skin conductance, and respiration (rate and volume). Historically, assessment of heart rate and skin conductance were prominent components of the behavior therapy movement. Contemporary assessment of anxiety, however, incorporates physiological monitoring only rarely, despite recent developments that permit ongoing monitoring of these processes outside of the laboratory setting (ambulatory monitoring using portable equipment).

Applications of Treatment

Psychological Treatments

There is considerable variability among psychological treatments for anxiety disorders. Those receiving the most empirical support, however, are cognitive-behavioral in nature. Cognitive-behavioral therapy (CBT) for anxiety disorders focuses on three common elements: promoting prolonged exposure to feared stimuli, reducing avoidance behaviors, and modifying maladaptive cognitions. The stimuli used for exposure and the particular cognitions addressed vary depending upon the disorder at hand and the patient. Many studies have shown that CBT produces outcomes that equal, and often exceed, those obtained with medication treatments. Unlike medication, CBT is usually time limited, has no side effects, and often provides longer-lasting benefit. CBT is thus now used frequently and is considered a first-line treatment for anxiety disorders.

Isaac Marks (1973) articulated the central role of therapeutic exposure by arguing that different behavioral treatments for anxiety were successful because they all promoted exposure to feared stimuli. Because the anxious individual’s typical response involves avoiding feared stimuli, exposure is beneficial presumably because it weakens the habitual anxiety response, promotes habituation to feared stimuli, and helps the patient realize that the feared outcome either will not occur or will be manageable. Thus, exposure progresses gradually and continues until the patient can tolerate the feared stimulus with minimal distress. Some individuals are understandably hesitant to confront the objects they fear. These concerns can be allayed in part by having the therapist first model the exposure exercise and then verbally reinforce the patient’s progress.

More recent influence from cognitive psychologists and theorists has prompted clinicians to attend more closely to the role of maladaptive thinking patterns in maintaining anxiety. Typically, these include deeply held core beliefs regarding danger and vulnerability in the world, irrational assumptions about the likelihood of the occurrence of negative events, and perceptions that negative events are much more catastrophic and unmanageable than they actually are.

Contemporary treatments for many anxiety disorders (PD, GAD, PTSD) thus often include an emphasis on “cognitive restructuring,” or modifying these maladaptive cognitions, in addition to exposure-based work. (More details on the basic principles of cognitive-behavioral therapy can be found in Chapter 87.) A few applications of these principles to the specific anxiety disorders will be considered here.

For PD patients, exposure targets feared bodily sensations that accompany panic attacks (interoceptive exposure) and agoraphobia-related situations. Cognitive restructuring is accomplished by educating the patient about the relative harmlessness of panic attacks and logically challenging beliefs that bodily sensations of anxiety are dangerous. Relaxation training and diaphragmatic breathing may be used as adjunct treatments to reduce the physiological arousal associated with chronic hyperventilation. Treatment of OCD typically arranges for exposure to feared stimuli that are related to the patient’s primary obsessions while prohibiting the compensatory compulsions (exposure and response prevention); cognitive restructuring may or may not be included. A patient with contamination obsessions, for example, might be instructed to handle “contaminated” objects (e.g., items in a trashcan, dirty clothes) repeatedly while refraining from hand washing. Psychological treatments for GAD often include some combination of the following: relaxation training to reduce chronic hyperarousal, imaginal exposure to worry themes and feared outcomes, “behavioral experiments” that test the accuracy of negative predictions, cognitive restructuring regarding the perceived usefulness of chronic worry, and training in active coping skills. PTSD treatments primarily emphasize in vivo or imaginal exposure to cues associated with the original trauma (e.g., returning to the scene of an accident, retelling an incident of war combat or sexual assault). Exposure treatments for PTSD are sometimes supplemented by efforts to modify newly developed negative beliefs about trust and safety. Treatments for phobias are relatively straightforward and focus primarily on exposure-based components, often administered in group therapy formats for socially phobic individuals.

Medication Treatments

Numerous medications have been used effectively with individuals who have been diagnosed with anxiety disorders. Two classes are used most frequently: benzodiazepines and selective serotonin reuptake inhibitors (SSRIs). Benzodiazepines are typically used for the temporary relief of acute anxiety conditions (such as occasional panic attacks). They produce sedation, reduce fear, and relax muscles, presumably through enhancing GABA, an inhibitory neurotransmitter. Because long-term use may lead to abuse and dependency, benzodiazepines are usually prescribed for short-term use or avoided in favor of the SSRIs. Common benzodiazepines include alprazolam (Xanax), clonazepam (Klonopin), and diazepam (Valium).

Compared to the benzodiazepines, the SSRIs are much less prone to abuse and dependency. They are thus often used for the long-term management of chronic anxiety conditions such as social phobia, PD, and OCD. Used also to treat depression, SSRIs increase the action of the neurotransmitter serotonin by blocking its reuptake into the presynpatic neuron. Sexual side effects are common, including reduced sexual desire, erectile dysfunction, and difficulty achieving orgasm. Common SSRIs include fluoxetine (Prozac), paroxetine (Paxil), sertraline (Zoloft), and escitalopram (Lexapro).


The Relationship between Anxiety and Depression

Interest in how we should conceptualize anxiety and fear has been paralleled by interest in the relationship between anxiety and depression. Similarities between these two concepts can be traced back to “neurosis,” a vague diagnostic term used decades ago to refer to psychological problems that were not severe enough to prevent an individual from thinking rationally. Since then, work by Clark and Watson (1991), among others, has focused on describing the differences and similarities between anxiety and depression. Their tripartite model indicates that both anxiety and depression share the general feature of negative affect, which refers to symptoms of distress and unpleasant emotions associated with both conditions: negative moods, difficulty concentrating, sleep problems, and irritability. Depression is distinguished from anxiety by the presence of low positive affect, which refers to the inability of depressed individuals to experience pleasure and positive emotions. Although anxious individuals still experience positive emotions, they manifest physiological hyperarousal, or elevated activity of the sympathetic nervous system as described earlier (and typically not characteristic of depression). The realization that depression and anxiety share the common feature of negative affect has spurred a tremendous amount of research. Negative affect may represent a vulnerability factor for the development of both disorders and may account, in part, for the comor-bidity between anxiety and depressive disorders.

Neurobiology and Anxiety

A detailed discussion of the multiple neurobiological influences on anxiety is well beyond the scope of this chapter. A general and admittedly simplistic overview will suffice.

Family, twin, and animal studies have confirmed the notion that anxiety has a genetic component. As described in Barlow’s model earlier, what is inherited does not appear to be the specific anxiety disorder itself, but rather a nonspecific genetic vulnerability toward anxiety. One exception to this nonspecific heritability is the fact that some phobias appear to be “biologically prepared” (Ohman & Mineka, 2001; Seligman, 1971). That is, humans most easily acquire fears of specific animals and situations that posed survival threats to our ancestors (e.g., snakes, heights, enclosed places).

Early research on the neurobiology of anxiety and fear focused primarily on single neurotransmitters: norepinephrine (specifically that within the locus ceruleus of the pons), serotonin, and GABA. Later came the realization that all these neurotransmitters were involved in various ways, and thus multiple brain structures and pathways were also involved. Among these, the limbic system (particularly the amygdala) plays a prominent role in fear by detecting threatening stimuli and producing fear responses. The pathway between the hypothalamus, pituitary gland, and adrenal gland (HPA axis) has been implicated more recently. Interactions within the HPA axis regulate the body’s response to anxiety and stress by releasing stress hormones such as cortisol and corticotropin-releasing hormone (CRH). The HPA axis, in turn, is regulated in part by the neurotransmitters already mentioned. Ultimately, though, fear and anxiety are whole-brain events that cannot be isolated to one or two neurotransmitters, structures, or pathways. As technology advances, future research will better clarify the contributions of the many brain structures and systems that are involved.

Future Directions

Despite recent advances in the assessment and treatment of anxiety, much work remains to be done. Much of this work will likely occur in neurobiology as scientists attempt to identify “biological markers” of anxiety, or the biological substances/anomalies that indicate the presence of or predisposition for a specific anxiety disorder. Geneticists will play an integral role in this effort as they attempt to isolate particular genetic contributions to the development of anxiety disorders. Advances in neuroimaging technology will further refine understanding of the involved brain structures. Cumulatively, these developments will be used to refine the complex multidimensional models described earlier.

Other directions of research lie within realm of clinical practice. Because many patients present to their primary care physicians with anxiety-related complaints, future studies should focus on developing more effective methods to assess anxiety disorders within medical settings. Other individuals receive inappropriate treatments that are not based on sound empirical research, highlighting the need for broader dissemination of cognitive-behavioral treatments and appropriate medication regimens. Still others do not present for treatment at all; mass communication efforts are needed to inform them that anxiety disorders are very treatable.

Similarly, the next several decades will continue to witness an emphasis on delivering psychological treatments in a time-efficient and cost-effective manner. This emphasis will be reflected in efforts to condense complex interventions into briefer protocols, to develop interventions that involve minimal therapist contact and can be presented using advanced information technology, and to disseminate these interventions to rural and underserved communities. Additionally, more research is needed on the efficacy of psychological treatments for individuals with comorbid diagnoses. Some of this research has already begun. For example, David Barlow and his colleagues (2004) are attempting to combine the major components of CBT into a unified treatment protocol, which potentially could be adapted to treat any emotional disorder (depression and/or anxiety disorders). These efforts are future directions in the sequence of scientific progress, not endpoints.


Conceptualizations of anxiety disorders have advanced considerably over the last several decades. Current multidimensional models attempt to relate the cognitive, behavioral, and physiological/neurobiological aspects of anxiety disorders to factors that contribute to the development and maintenance of anxiety disorders. Despite their differences, the major anxiety disorders are all characterized by prominent fear or anxiety and some element of avoidance behavior. Various self-report, behavioral, and physiological assessment strategies are available to assess the major components of each anxiety disorder. Treatment is guided by the disorder(s) at hand as well as the constellation of the patient’s symptoms. Although the procedural details vary, psychological treatments for anxiety are grounded in the common strategies of arranging for prolonged exposure to feared stimuli, reducing avoidance behavior, and modifying maladaptive patterns of thinking. Much work remains in understanding the complex neurobiological substrates of anxiety, addressing anxiety within medical settings, and developing and disseminating interventions.