Epidemiology and impact of OCD. OCD is currently defined as an anxiety disorder in DSM-IV, and is one of the most incapacitating conditions according to the World Health Organisation. The widely agreed criteria for diagnosis require that the individual have either obsessions or compulsions or both. Obsessions are recurrent, persistent ideas, thoughts, images or impulses that intrude into consciousness and are experienced as senseless or repugnant. They occur against the individual’s will and typically the individual attempts to resist or get rid of them. In contrast to psychotic phenomena, the individual realises the thoughts are their own. They typically cause marked anxiety, distress or discomfort, which is particularly important in understanding OCD’s phenomenology given that intrusive thoughts with potentially distressing content occur frequently and without causing distress in large percentages of the population (Xxxxxxx and xx Xxxxx 1978). There has been much work on the nature of ‘clinical’ and ‘nonclinical’ obsessions, and another distinction made between clinical obsessions and normal intrusions is that the former are more persistent, more repetitive, cause distress and are harder to remove. Compulsions are repetitive, purposeful forms of behaviour carried out because there is a strong drive or urge to do so. The compulsive behaviour is designed to prevent or reduce anxiety or discomfort or to prevent a dreaded event or situation. Although OCD can occur with a lack of insight, affected individuals typically realize their compulsions are excessive. There is much research and debate concerning subtypes of OCD, multidimensional approaches to symptoms and OCD-related spectrum conditions although this will not be addressed explicitly in this thesis. Lifetime prevalence of OCD is thought to be between 1-4% of the general population (Xxxxxxxx, Xxxxx et al. 1994; Xxxxxx 2006). It is a chronic disorder where there are often some features in childhood (Xxxxx, Xxxxxxxx et al. 2001; Xxxxxx, Mataix-Cols et al. 2006). OCD that begins in childhood is associated with a higher risk of other psychiatric disorders in adult life, including other anxiety disorders and affective disorders (Xxxxxxxx, Xxxx et al. 2001). However there are significant methodological difficulties with some of this research concerning the onset of actual OCD and common ‘symptoms’ which may be found in large proportion of the population that do not go on to develop into OCD or put them at elevated risk. Similarly there is a...
