The current study examined the relationship between measures of trait vulnerability and long-term outcome in 83 patients diagnosed and treated for Generalized Anxiety Disorder (GAD) 8–14 years previously. Diagnostic status was assessed by structured interview, and trait affect, trait anxiety and trait depression were measured by the Positive and Negative Affect Scale (PANAS), the State–Trait Anxiety Inventory (STAI-T) and the Personal Style Inventory (PSI), respectively. Trait measures were all highly inter-correlated, and patients with diagnoses of GAD, social phobia and depressive disorders at long-term follow-up recorded very poor scores on all three scales. Trait anxiety recorded pre-treatment was also related to both anxiety and depression at long-term follow-up. However, trait depression showed no significant association with panic disorder. Increased numbers of comorbid diagnoses were strongly related to high levels of both trait anxiety and negative affect (NA). The findings suggest that patients reporting high trait anxiety or NA may suffer from a chronic course of disorder and higher levels of comorbidity over the longer term.
Despite the recent tendency for greater differentiation in the diagnosis of neurotic disorders and the introduction of new disorders (such as panic) to DSM-III-R (APA, 1987), there remains a large body of support for the notion of a general vulnerability to psychological distress, which makes the patient susceptible to symptoms of both anxiety and depression. Tyrer (1985) suggested that patients with this general neurotic tendency are likely to have a poorer response to treatment, fluctuate between anxiety and depressive diagnoses, and follow a relapsing and/or chronic course of disorder over the longer term.
Evidence for such general vulnerability comes from a variety of sources. Firstly, comorbidity studies have found a strong overlap between anxiety and depressive diagnoses. In one such study, Andrews, Stewart, Morris-Yates, Holt, and Henderson (1990) examined comorbidity of lifetime neurotic diagnoses in both patient and general population twin samples, and reported that levels of comorbidity found in both groups were significantly higher than could be expected from the observed occurrence of each individual diagnosis. For example overall prevalence of a lifetime diagnosis of depression in the sample of 892 twins was 7%, whereas prevalence of lifetime depression in those also receiving a lifetime diagnosis of GAD was 26%. They also found that individuals receiving a lifetime diagnosis of anxiety or depressive disorders had higher levels of neuroticism (as measured by EPQ N; Eysenck, 1967) and lower levels of perceived control as compared to a population sample. Further, as neuroticism and locus of control did not distinguish between diagnoses in this study, it was proposed that the concept of a General Neurotic Syndrome could be explained in part by the presence of these vulnerability factors. Genetic studies have not only supported this overlap between neuroticism, anxiety, and depressive symptoms, but have also suggested there is a strong genetic component which is common to all three. For example, in a study of 3810 twins, Jardine, Martin, and Henderson (1984) compared neuroticism with anxiety and depressive symptoms and found that genetic factors accounted for 50% of the variation in neuroticism, 38% of the variation in anxiety symptoms and 36% for depressive symptoms. Using a multivariate genetic analysis, they concluded that the same genes which determined the variation in neuroticism were also responsible for the genetic variation in anxiety and depressive symptoms.
