Norman and Olver anxiety/worry present was unrelated to it. DSM-IV further reﬁned the diagnostic criteria of GAD by exclusion of auto- nomic symptoms from the list of somatic concerns required for diagnosis because of the low endorsement rate of these symptoms. The core features of the current deﬁnition of GAD revolve around uncontrollable and excessive worry. The worries experienced by patients with GAD reliably cluster around themes of family, ﬁnances, work and personal illness (Sanderson and Barlow 1990). The alternate ICD-10 classiﬁcation also recognises GAD as a separate disorder of chronic duration (6 months) but differs from DSM-IV with respect to the pervasiveness of the symptomatology. Thus ICD-10 does not require worry to be excessive or uncontrollable while there is an emphasis on autonomic hyper-arousal. Further a minimum of four symp- toms from a list of 22 somatic symptoms must be present to meet diagnostic criteria. The differences in diagnostic schemes lead to rather dif- ferent estimates of prevalence depending on which one is used for diagnosis. Nevertheless various epidemiological studies, using the different criteria, suggest that GAD is a common psychiatric presentation with estimates of lifetime prevalence of 2.8% to 6.6% in the general population (Carter et al 2001; Kessler et al 2005). The 12-month prevalence of any anxiety disorder in the National Co-morbidity study conducted in 9,282 adults in the United States was 18.1% (Kessler et al 2005). In this cohort the 12-month prevalence for GAD was 5.7%. This ﬁgure is in reasonably close agreement to a number of epidemiological studies conducted in the European com- munity (Lieb et al 2005). The lifetime prevalence of GAD ranged from 0.1% to 18.7%, while 12-month prevalence was reported as 0.1% to 2.1%. Discrepancies between surveys can be accounted for by the different diagnostic criteria employed (DSM-III, DSM-IV or ICD-10) and the different instruments used to asses anxiety (CIDI or DIS in most studies). Where DSM-III criteria were employed prevalence is usually higher due to the shorter duration requirement. The antecedents of GAD are in all likelihood present in childhood but some studies suggest that the age of onset of the disorder is rare before the age of 20 years (Wittchen et al 1998; Lieb et al 2000). The majority of cases present for treatment in adult- hood between 35 and 45 years of age (Wittchen et al 2000; Yonkers et al 2000; Carter et al 2001). Furthermore GAD has been reported to be the most common anxiety disorder in adults aged more than 55 years (Carter et al 2001). Guidelines for the treatment of GAD recommend psy- chotherapy, pharmacotherapy or the combination of both (Anderson 2006). The NICE (National Institute of Clinical 1170 Excellence, UK) guidelines indicate that psychotherapy should be ﬁrst line treatment (NICE 2004). It is generally regarded that medication and psychotherapy are equally effective for acute treatment (Anderson 2006; Tyrer and Baldwin 2006). Indeed a meta-analysis of 35 studies showed that the effect size for cognitive behavior therapy (0.7) was similar to that for medications (0.6) (Gould et al 1997). Among the psy- chotherapies there is some evidence that cognitive behavior therapy has a better outcome at 6-month follow-up than anxiety management or analytical psychotherapy (Durham et al 1994). In longer term treatment psychological treatments might be better than medications but there are few compara- tive data. Improvement with cognitive behavior therapy can be maintained for up to 2 years (Kingdon et al 1996). In longer follow-ups (8–14 years), only about a third of patients make a good recovery (Durham et al 2003). Considerations of the characteristics of GAD and the preferences of individual patients need to be taken into account when deciding treatments (Lam 2006). Particular issues pertaining to the clinical characteristics of GAD are the waxing and waning course of the illness, its chronicity and co-morbidity with other psychiatric and non-psychiatric disorders. Additionally prospective data suggest that GAD has a relatively low rate of remission. Thus in the Harvard-Brown Anxiety Research program (HARP) the probability of remis- sion was 0.38 at 5 years (Yonkers et al 2000). In the 5-year follow-up period 38% of patients achieved a full remission, ie, a consecutive 8-week period with no or only occasional symptoms. The prognosis must be regarded as unfavorable. Patients with GAD commonly present with a co-existing depressive disorder (Baldwin and Polkinghorn 2005). Indeed based on the results of the National Co-morbidity Survey (Kessler et al 1994) it might be stated that co-morbidity is the rule rather than the exception. For GAD the total lifetime co-morbidity with another psychiatric diagnosis was 90.4% and the 30-day co-morbidity was 66.3% with the following disorders: mania, major depression, dysthymia, panic disor- der and phobic disorders, alcohol or drug abuse (Wittchen et al 1994). This high co-morbidity has been used to suggest that GAD may be a residual or prodrome of another disorder (Wittchen et al 1994). On the other hand about a third of subjects with a current diagnosis of GAD did not have any other recent diagnosis in the National Co-morbidity study, which argued for GAD as an independent diagnostic category (Wittchen et al 1994). For the short term treatment of GAD benzodiazepines have been shown to be more effective than placebo (Shader and Greenblatt 1993; Ballenger 2001; Davidson 2001; Baldwin Neuropsychiatric Disease and Treatment 2008:4(6)