Introduction

Obsessive–compulsive behaviour has long been described; religious scrupulosity is documented in medieval texts (Adams, 1973), repetitive hand washing as symbolic of guilt has been depicted by playwrights (Shakespeare: Macbeth) and ‘obsessive–compulsive neurosis’ generated by unconscious conflict was a cornerstone of psychodynamic theory (Freud, 1973). More recently, however, a new paradigm has emerged; obsessive–compulsive behaviour is now viewed as symptomatic of a highly prevalent medical disorder, characterized by specific psychobiological dysfunctions. Indeed, obsessive–compulsive disorder (OCD) is arguably one of the most incisive exemplars of a neuropsychiatric disorder, insofar as clear models now exist of how its characteristic psychopathology is mediated by specific neuroanatomical circuits and neurochemical systems. This chapter aims to provide a comprehensive review of the current state of knowledge on OCD, including epidemiology, clinical features, neurobiology and management.

Epidemiology

Prevalence

Until the 1980s OCD was viewed as a rare disorder, which only affected 0.005% of the population. These figures were based on a study by Rudin, which looked at the prevalence of OCD in a psychiatric in-patient population (Rudin, 1953). The Epidemiological Catchment Area (ECA) study of 1980–1984 radically changed views of the prevalence of OCD (Karno et al., 1988). Undertaken in five US communities, this study found lifetime prevalence rates for OCD to be 1.9–3.3%, making it the fourth most common psychiatric disorder, with a prevalence that was 25–60 times higher than previously believed. These figures were subsequently confirmed in similar studies in Canada (Kolada et al., 1994), Taiwan (Hwuh & Chang, 1989), and several other countries (Weismann et al., 1994), demonstrating that OCD is a disorder with a similar prevalence across nationalities.

The ECA figures, however, have been challenged. The ECA and cross-national study used the Diagnostic Interview Schedule (DIS); a structured interview designed for trained lay interviewers, to arrive at diagnoses. Several later studies have questioned the validity of DIS diagnoses. Nelson and Rice (1997) examined the 1-year temporal stability of the DIS and found it to be low, with only 19.2% of those who were originally diagnosed with OCD having this diagnosis confirmed on follow-up interview. Two follow-up studies of the ECA, using semistructured interviews conducted by psychiatrists (Antony et al., 1985; Helzer et al., 1985), supported these findings. However, these studies have been criticized in view of their small sample size and failure to use objective instruments to ascertain the diagnosis of OCD.