Generalised Anxiety Disorder Health Article

Prevalence And Comorbidity

The high prevalence of concurrent psychiatric disorders is the most damaging criticism of the diagnosis of generalised anxiety disorder (and many other anxiety disorders). Epidemiological studies in Europe suggest that the illness has a lifetime prevalence of 4·3–5·9% and a probable 12-month prevalence of 1·2–1·9%. Comorbidity with major depression is present in three out of five cases and a similar proportion have other anxiety disorders. ⁴² Only two out of five patients seek treatment for their disorders ⁴³ and for these patients the rates of full or partial remission in the long term (5 years or more) are fairly disappointing at 38–41%. Comorbidity with personality disorder is a major handicap to recovery. ^44,45 Comorbid diagnosis is associated with greater social and occupational impairment than generalised anxiety disorder alone and also confers a worse prognosis. ^45,46 Attempts have been made to regard primary generalised anxiety disorder (ie, when generalised anxiety disorder is the initial illness that the patient has diagnosed) ^47,48 as fundamentally different from the secondary equivalent; comorbidity during follow-up is increased for secondary generalised anxiety disorder. ⁴⁹ The association of anxiety with depressive symptoms is the most difficult aspect for the clinician in forming a diagnosis. This combined disorder, which has been called “cothymia”, ⁵⁰ is given separate status in ICD-10 as “mixed anxiety and depressive disorder”, but only when “neither type of symptom is present to the extent that justifies a diagnosis if considered separately”. ¹¹ However, even using this restricted definition, mixed anxiety and depressive disorder is by far the most common mental disorder in epidemiological surveys and raises the 1-week prevalence of neurotic disorder to one in eight in men and one in five in women. ⁵¹

The personality trait neuroticism, or negative affectivity, characterises the link between anxiety and depression. ⁵² Neuroticism seems to develop early in life and has led to the suggestion that the highly comorbid anxiety and depressive disorders, together with a dependent, avoidant, or obsessional personality, are part of a general neurotic syndrome ^8,53,54 and should be separated from single disorders that are often self-limiting and have a reasonable outcome. However, even after comorbidity is taken into account, a core generalised anxiety disorder associated with substantial social dysfunction still exists. ^42,55,56 Generalised anxiety disorder is now accepted as an illness that results in substantial morbidity and leads to poor quality of life. ^57,58

Outcome

Generalised anxiety disorder is typically regarded as a chronic illness. Most patients are still highly affected 6–12 years after diagnosis, ^44–45 and in one study, personality disorders showed less stability and greater improvement over 2 years than all anxiety disorders. ⁵⁹ Most of these studies were done in affluent countries with wide access to treatment and even here, long-term morbidity remains high. One of the problems in assessment of outcome is determination of the role of concurrent disorders such as hypochondriasis, ⁶⁰ social anxiety disorder, ⁶¹ or avoidant personality disorder. ⁶² Avoidant personality disorder itself is very difficult to distinguish from generalised social phobia, ⁶³ and so the negative outcome could be as much a consequence of generalised anxiety disorder acting as a precursor of these other disorders as from the original anxiety disorder.

There are no specific associations between anxiety and other physical disorders–the association with thyrotoxicosis is often cited but the anxiety in this disorder is often recognised as qualitatively different from other spontaneous anxieties. Mortality is raised in patients with generalised anxiety disorder, ⁶⁴ but not specifically from suicide. ⁶⁵ The cost of care for generalised anxiety disorder is high because of its chronic nature, although the cost (mainly of consultations with non-psychiatric clinicians) is less than that of panic disorder or post-traumatic stress disorder. ⁶⁶ The cost of treatment for anxiety with comorbid depression or general neurotic syndrome is nearly twice that of a single diagnosis of generalised anxiety disorder. ⁶⁷