In recent years, there has been a renewed interest in obsessive-compulsive disorder (OCD) among psychiatrists due to several factors. OCD is not a rare disease as was believed in former times. New epidemiological studies demonstrate that 1–2% of the adult population suffer from OCD. This result was confirmed by several epidemiological studies among different cultural environments which are summarised by Dr Bebbington in this supplement. Thus, OCD figures among the most common of mental disorders. Lately a unique category of disorders has emerged that share some common key features with OCD. These ‘obsessive-compulsive spectrum disorders’ and their treatments are characterised in Dr Hollander's paper.

Background Although the concept of obsessive-compulsive disorder (OCD) has long been established, research diagnostic criteria are relatively recent developments. This is partly because the symptoms of OCD occur in the context of other disorders and it is arguable to what extent they are relatively discrete phenomena.

Method Review of the existing epidemiological surveys based on standardised instruments.

Results Nine population surveys using the Diagnostic Interview Schedule have given data on OCD, with six-month prevalences ranging from 0.7 to 2.1%. The British National Survey of Psychiatric Morbidity based on the CIS – R gave a one-month prevalence of 1% in males and 1.5% in females. Community surveys show an excess of females and emphasise the early age of onset. Minor obsessional symptoms are considerably more common than OCD itself.

Conclusions OCD is fairly rare in the general population, but causes considerable distress to those who suffer from it.

Background Obsessive-compulsive spectrum disorders (OCSDs) are now recognised as distinct diagnostic entities related to obsessive-compulsive disorder (OCD). The features of OCSDs and OCD overlap in many respects including demographics, repetitive intrusive thoughts or behaviours, comorbidity, aetiology and preferential response to anti-obsessional drugs such as the selective serotonin reuptake inhibitors (SSRIs).

Method Literature was reviewed and preliminary data from various studies were re-examined to assess the relationship between compulsivity and impulsivity, and between OCD and OCSDs.

Results OCSDs include both compulsive and impulsive disorders and these can be viewed as lying at opposite ends of the dimension of risk avoidance. Compulsiveness is associated with increased frontal lobe activity and increased serotonergic activity, while impulsiveness is associated with reduced activity of these variables. Neural circuits affected by serotonergic pathways have been identified and pharmacological challenge of OCSD patients with serotonin receptor agonists have supported the involvement of serotonergic processes.

Conclusions SSRIs such as fluvoxamine have established efficacy in OCD and preliminary studies indicate that they are also effective in OCSDs. The features of three specimen OCSDs –body dysmorphic disorder, pathological gambling and autism – and their treatment with SSRIs are reviewed.

Background Serotonin may play a role in the pathophysiology of obsessive-compulsive disorder (OCD) because of the anti-obsessional effect of selective serotonin reuptake inhibitors (SSRJs).

Method The literature is reviewed on knowledge of the role of serotonergic neurons in brain function, studies on monoamine metabolites in cerebrospinal fluid (CSF), various stress neuropeptides, neuroendocrine and behavioural challenge after administration of direct and indirect serotomimetic compounds, and neuroanatomical data on brain circuits organising behaviour.

Results In most of the OCD cases analysed, CSF 5-hydroxyindoleacetic acid and homovanillic acid concentrations do not significantly differ from age-corrected controls. However, a relationship appears to exist between pre-treatment levels of these metabolites and clinical response to drugs acting on the serotonin transporter. Abnormalities in CSF arginine vasopressin, corticotropin-releasing hormone, oxytocin and somatostatin levels have been reported in OCD. Long-term treatment with high-doses of clomipramine, fluvoxamine, and fluoxetine tend to correct these neuropeptide abnormalities.

Conclusions We hypothesise that continuous treatment with SSRJs alters serotonin turnover and neuropeptide expression patterns in OCD-entertaining functional forebrain/midbrain circuits.

Background There is a major role for serotonin in the mechanism of anti-obsessional drug action. Drugs that block uptake of noradrenaline are not effective in the treatment of obsessive-compulsive disorder (OCD), while drugs that potently bock serotonin reuptake are effective. While enhancement of serotonin neurotransmission is clearly involved in the treatment of OCD, the role of serotonin in the pathophysiology of OCD is less clear.

Method This paper provides a brief, focused review ofthe literature regarding treatment of OCD, the effects of drugs with selective action at various serotonin receptors and results of neurotransmitter depletion studies in patients with OCD.

Results Some patients with OCD may experience remission of OCD symptoms during intoxication with psychedelic drugs that have potent 5-HT2A/2c agonist activity. These findings, coupled with results from serotonin depletion studies in depressed and OCD patients, suggest that enhancement of serotonin neurotransmission may underlie both antidepressant and anti-obsessional drug action, although the targeted brain areas may differ.

Conclusions OCD may not involve a dysfunction ofthe serotonin system. Rather, it is more likely to involve a dysfunction of specific brain circuits, particularly in the frontal cortex. Modulation of these circuits by serotonin neurons may underlie the specific action of anti-obsessional drugs.

Background Neuroimaging studies provide strong evidence that the pathophysiology of obsessive-compulsive disorder (OCD) involves abnormal functioning along specific frontal-subcortical brain circuits.

Method A literature search was carried out for all brain imaging studies of patients with OCD. We also reviewed the basic science literature on the functional neuroanatomy of cortico-basal ganglia circuits, and integrated this information with neuroimaging data in OCD to formulate a theoretical model of brain mediation of OCD symptoms and response to treatment.

Results At least a subgroup of patients with OCD may have abnormal basal ganglia development. Functional neuroimaging studies indicate that OCD symptoms are associated with increased activity in orbitofrontal cortex, caudate nucleus, thalamus and anterior cingulate gyrus.

Conclusions OCD symptoms are mediated by hyperactivity in orbitofrontal-subcortical circuits, perhaps due to an imbalance of tone between direct and indirect striatopallidal pathways. We present a model which describes how frontal-subcortical brain circuitry may mediate OCD symptomatology, and suggest a hypothesis for how successful treatments may ameliorate symptoms, via their effects on circuit activity.

Background Recent research has demonstrated that cognitive-behavioural therapy (CBT) for obsessive-compulsive disorder (OCD) can systematically modify cerebral metabolic activity in a manner which is significantly related to clinical outcome.

Method A substantial body of research is reviewed which supports an involvement of neural circuitry connecting the orbitofrontal cortex, cingulate gyrus and basal ganglia in the expression of the symptoms of OCD.

Results Data are presented which expand upon previous work demonstrating effects of CBTon functional interactions between limbic cortex and the basal ganglia.

Conclusions The relevance of these effects of CBTon brain function is discussed in the context of recent advances in our knowledge of cortical–basal ganglia physiology. The clinical importance of these data is best appreciated when they are seen to reflect the interactive nature of the relationships between cognitive choice, behavioural output and brain activity.

Background With regard to long-term outcome, behaviour therapy is the first choice treatment for obsessive–compulsive disorder (OCD), with or without concomitant selective serotonin reuptake inhibitor (SSRI) medication. Yet, results from research trials, usually restricted to exposure with response-preventions and other symptom-directed techniques, may not be generalisable to people with OCD in community health care services.

Method For more than 20 years we have delivered out-patient behaviour therapy to unselected people with OCD from the community, including those with motivational and compliance problems. Prospective–retrospective follow-ups were carried out from 1–13 years after treatment.

Results This paper describes the applied multimodal, strategic-systemic behaviour therapy, and our partially new model of OCD. Compliant patients achieved the usual success rate of 65–70%, but this drops to 50% if all patients treated are included in the analysis.

Conclusions For major subgroups of OCD, behaviour therapy is a very effective treatment modality. Exposure is essential, but additional (‘causal’) interventions are equally important in about half of the patients from unselected samples. Both behaviour therapy and drug-treatments need to be improved and predictive variables for outcome of either of them are urgently needed.

Background Obsessional ruminations (obsessions without any accompanying overt compulsive behaviour) were previously considered especially difficult to treat.

Method Cognitive-behavioural theory regarding obsessional problems is discussed. Strategies for therapy developed on the basis of this theory are reviewed.

Results The cognitive-behavioural theory of obsessive-compulsive disorder proposes that obsessional problems occur as a consequence of the particular meaning or significance which patients attach to the occurrence and/or content of intrusive thoughts. When intrusions are interpreted (appraised) as indicating increased personal responsibility, this results in both distress and the occurrence of neutralising behaviour. Cognitive-behavioural treatment seeks to change responsibility beliefs and appraisals, and thereby reduce distress and eliminate neutralising responses which usually occur as covert neutralising (mental rituals). Evidence is emerging for the success of therapy developed on this theoretical basis.

Conclusions Recent developments in the psychological conceptualisation of obsessional ruminations have improved the prospects for successful therapy.

Background Pharmacotherapy for obsessive-compulsive disorder (OCD) was seldom beneficial before clomipramine, a potent selective serotonin reuptake inhibitor (SSRI), became available. Subsequent progress in pharmacotherapy for OCD has increased the possibility of effective treatment for most sufferers.

Method Randomised controlled trials of pharmacotherapy for OCD were reviewed, as well as reports of beneficial pharmacotherapy found in open trials and case reports.

Results SSRIs are well-tolerated by patients with OCD, even in large doses. Prose roto n erg i c augmentation is seldom helpful but antipsychotic augmentations seem beneficial for many OCD patients with comorbid tics.

Conclusions Potent SSRIs are the pharmacotherapy of choice for OCD, with a more limited role reserved for monoamine oxidase inhibitors. If one SSRI is ineffective, others may be beneficial. Non-drug therapies are also important in OCD: behaviour therapy is frequently helpful but infrequently available and neurosurgery is sometimes helpful when all other treatments have failed.

Background We investigated whether the combination of multimodal behaviour therapy (BT) with fluvoxamine is superior to BTand placebo in the acute treatment of severely ill in-patients with obsessive-compulsive disorder (OCD).

Method In a randomised, double-blind design, 30 patients were treated for nine weeks with BT plus placebo and 30 patients with BT plus fluvoxamine (maximum dosage 300 mg, mean dose 288.1 mg). BT included exposure with response prevention, cognitive restructuring and development of alternative behaviours.

Results Both groups showed a highly significant symptom reduction after treatment. There were no significant differences between the groups concerning compulsions. Obsessions were significantly more reduced in the fluvoxamine and BT group than in the placebo and BT group. Furthermore, the group BT plus fluvoxamine showed a significantly higher response rate (87.5 v. 60%) according to a previously defined response criterion. Severely depressed patients with OCD receiving BT plus placebo presented a significantly worse treatment outcome (Y–BOCS scores) than all other groups.

Conclusions The results suggest that BTshould be combined with fluvoxamine when obsessions dominate the clinical picture and when a secondary depression is present.

Background Case reports suggest that neurosurgical operations can improve symptoms in patients with severe treatment-refractory obsessive-compulsive disorder (OCD). However, it is unclear which procedure is best and which may produce the most side-effects.

Method I review the literature on the efficacy and complications of four frequently used neurosurgical procedures (cingulotomy, capsulotomy, limbic leucotomy and subcaudate tractotomy) that are used to treat refractory OCD.

Results Since the vast majority of patients who underwent surgery were severely and chronically disabled, it is likely that these procedures were of assistance in alleviating some of their symptoms. It is currently impossible to determine which surgical procedure is the best for a particular patient.

Conclusions Despite a lack of controlled data and inconsistencies in the literature, it appears that when nonsurgical treatments have failed to improve OCD symptoms significantly in severely ill patients, at least partial relief can be obtained by some people with OCD by neurosurgery Results of cumulative studies strongly support the need for continued research in this area.

Background Obsessive-compulsive disorder (OCD) is a common psychiatric condition that usually emerges during childhood or adolescence. Over 80% of individuals with OCD have their onset before age 18 years. Epidemiologic studies suggest a prevalence of 1 -2 for adolescents.

Method This article reviews current knowledge of paediatric OCD in the following areas: age of onset, nosology and classification, subtypes, prevalence, aetiology, pathophysiology, assessment, prognosis and treatment.

Results Essential components of treatment include long-term commitment, care management and illness education. Specific components of treatment include cognitive-behavioural therapy, parent behaviour management training and medication.

Conclusions The most effective treatments are selective serotonin reuptake inhibitors (e.g. fluvoxamine, sertraline) and exposure/response prevention.