It follows that in spite of the apparent evidence, extreme caution should be exercised when interpreting the epidemiology of anxiety.
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%.
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).
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).
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).
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.
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
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.
Comparative studies of treatment or, even supposedly more objective physiological investigations, carried out by single-minded enthusiasts are inferior to collaborations between scientists with opposing views who are willing to put them to the test.]]>