Epidemiology of Anxiety Disorders
Epidemiology of Anxiety Disorders - Conclusion
The authors would like to end by the beginning, referring to the caveats in the introduction of the present chapter. There are still other matters of concern: the frequent use of lay interviewers in major surveys, recall bias in interviews over lifetime span, the key issue of defining a threshold for clinical significancy, just to name a few.
It follows that in spite of the apparent evidence, extreme caution should be exercised when interpreting the epidemiology of anxiety.
Post-Traumatic Stress Disorder (PTSD)
The DSM-IV definition for PTSD contains criteria for (a) the traumatic experience; (b) re-experiencing; (c) avoidance of associated stimuli and numbing; and (d) increased arousal. Duration of symptoms should be at least one month (e); and (f ) distress or impairment in functioning is required (APA, 1994). When PTSD was first defined in DSM-III (APA, 1980), the original stressor criterion characterised traumatic experiences as being outside the range of human experience. However, when the prevalence of such events was systematically examined, it became apparent that trauma is surprisingly commonplace. Several studies have investigated the overall prevalence of traumatic events in the general population, looking both at communitybased populations and populations of individuals at high risk of trauma or exposed to events such as natural disasters (Acierno et al., 1999). The nature of the trauma can be very diverse, such as childhood abuse, traffic accidents, fires, violent assault, robberies and floods or earthquakes.
Prevalence
Prevalence rates have increased from DSM-III to DSM-III-R and DSM-IV. Also, in some telephone interview surveys prevalence is much higher, and in studies among young persons where recall bias may be minimal. Kessler et al. (1995) reported on the National Comorbidity Survey of 5877 persons, aged 15 to 54 years. The estimated lifetime prevalence of PTSD was found to be 7.8%.
Generalised Anxiety Disorder (GAD)
The concept of generalised anxiety disorder is subject to discussion. Although the disorder is regarded as prevalent in primary care as well as in specialised settings, because of the high comorbidity rates associated with GAD the controversy is about whether to consider GAD an independent disorder or as a residual or prodrome of other disorders (Wittchen et al., 1994). The diagnostic category of GAD has changed a lot in the past two decades (Brawman-Mintzer and Lydiard, 1996). The shifting diagnostic criteria, the relative low diagnostic reliability, and questions regarding the diagnostic validity probably contributed to the relative little attention that has been paid to the investigation of GAD compared with most other anxiety disorders.
Prevalence
The most recent epidemiological study using DSM-III-R criteria is the NCS in the United States. The prevalence rate for current GAD was 1.6%, 12-month prevalence was 3.1% and lifetime prevalence was 5.1% (Wittchen et al., 1994). These figures make GAD more common than panic disorder in the NCS. It is shown that GAD is more common in primary care, and one of the least common anxiety disorders in mental health centres (Brawman-Mintzer and Lydiard, 1996).
Obsessive-Compulsive Disorder (OCD)
Obsessive-compulsive disorder is defined as the presence of recurrent obsessions (persistent thoughts, impulses, or images) or compulsions (repetitive behaviour or thought patterns induced in an attempt to prevent anxiety) that are excessively time-consuming (taking more than an hour a day) or cause marked distress or significant impairment. The subject recognises that these patterns are excessive.
Differential diagnosis of obsessive-compulsive disorder includes generalised anxiety disorder, panic disorder, phobias, compulsive personality disorder, and hypochondriasis. While many of these syndromes are characterised by intrusive thoughts, few have associated rituals. The complex tics seen in some patients with Tourette’s syndrome may be difficult to distinguish from the compulsions seen in obsessive-compulsive disorder, and, in fact, there is significant overlap in symptoms between the two disorders (Rasmussen and Eisen, 1992).
Specific Phobias
Specific phobias are the second most common anxiety disorder, after social phobia.
They are, however, less impressive because they are mostly less incapacitating than other anxiety disorders. A specific phobia is defined as a circumscribed, persistent, and unreasonable fear of a particular object or situation. Exposure to this phobic stimulus is associated with an acute and severe anxiety reaction. Although individuals with specific phobias recognise their fear is unrealistic, most adjust their lifestyle so that they can completely avoid or at least minimise this contact (Fyer, 1998). Within the specific phobia category there is considerable heterogeneity. In the DSM-IV, four subtypes are defined, and animal phobias, situational phobias, blood-injury phobia, and nature-environment phobia are distinguished. The first three have been differentiated on the basis of a combination of factors including age at onset, symptom response, heritability and biological challenges (Fyer, 1998; Verburg et al., 1994). On the separate position of the nature-environment phobia there is less consensus (Fyer, 1998).
Social Phobias
In recent years social phobia has gained more professional and public interest and increasingly is being recognised as a real anxiety disorder for which treatment can offer an improvement of the patient’s quality of life (Kasper, 1998). Social phobia (social anxiety disorder) usually is rather disabling, characterised by marked fear of performance, excessive fear of scrutiny, and fear of acting in a way that may be embarrassing. Most patients are over-sensitive to the assumed opinion of others and have a low self-esteem, although they feel their fears are exaggerated and out of proportion. Going through the feared situations, or even anticipating them, most people suffer from physical symptoms like sweating, trembling or blushing, and these symptoms can become a trigger on their own to worry about social consequences.
This all can lead to avoidance of many social situations, or they endure these situations with extreme anxiety or distress (Liebowitz, 1999). As in all cases of phobias, the individual recognises that his or her fears are unreasonable.
Social phobia can be divided in two subtypes. The first is generalised social phobia (or complex social phobia), patients being anxious in most situations concerning performance and interactional situations. The patient with non-generalised social anxiety disorder is scared of only one or two (usual performance-related) social situations, such as public speaking, or other public performance, such as writing or eating in front of others (Moutier and Stein, 1999; Stein and Chavira, 1998). Both types, however, tend to be underdiagnosed and undertreated (Stein and Chavira, 1998). There are some differences between the subgroups, the generalised type has even less chance of spontaneous recovery than the non-generalised. In the generalised subtype there is a stronger genetic factor (Kessler et al., 1998b). The generalised subtype is usually more invalidating and carries a higher risk of comorbidity. Age of onset does not differ between the subtypes.
Epidemiology of Anxiety Disorders Introduction
Anxiety disorders have a high impact on daily life (illness intrusiveness) and cause a great deal of suffering for the individual patient (Antony et al., 1998). They also have a substantial impact economically and incur a great deal of expenditure by society as a whole. Greenberg et al. (1999) report a total of $42.3 billion per year as direct and indirect expenses in the USA and there are no obvious reasons to assume that the picture for European countries would be very different (Costa, 1998; Martin, 1998).
In the last decades some large epidemiological studies have provided much information about the occurrence of psychiatric disorders in general and anxiety disorders in particular. The Epidemiologic Catchment Area study (NIMH) and the
Panic Disorder and Agoraphobia
According to DSM-IV (APA, 1994) panic attacks are defined as sudden spells of unidentified feelings consisting of at least four out of 13 symptoms as palpitations, chest strains, sweating, shortness of breath, feelings of choking, trembling, nausea, dizziness, paresthesias, chills or hot flushes, depersonalisation or derealisation, fear of dying or losing control. Although having panic attacks does not imply that the diagnosis of panic disorder can be made and isolated panic attacks are not diagnosed as a disorder, they are often associated with substantial morbidity and do have some clinical significance (Klerman et al., 1991).
In order to make a diagnosis of panic disorder, additional criteria are that these attacks at least once have been unexpected, followed by at least one month of fearful expectation or concern about the consequences of an attack. In the DSM-IV criteria as to the frequency of the attacks (in DSM-III-R, APA 1987, three attacks in a period of three weeks) are abandoned.
Panic disorder is frequently followed (or accompanied) by agoraphobia. Agoraphobia in DSM-IV is defined as (a) fear of being in places or situations from which escape might be difficult or help might not be available; (b) these situations are avoided or endured with marked distress or the patient needs a companion; and (c) the fear is not better explained by another mental disorder.