OVERVIEW

Obsessive-compulsive disorder (OCD) is a common disorder that affects individuals throughout the life span. This disorder has been listed as one of the ten most disabling illnesses by the World Health Organization.¹ The National Comorbidity Survey Replication indicated that OCD is the anxiety disorder with the highest percentage (50.6%) of serious cases.² Putative OCD-related disorders (OCRDs) include somatoform disorders (e.g., body dysmorphic disorder [BDD] and hypochondriasis), tic disorders (e.g., Tourette’s disorder), and impulse control disorders (e.g., trichotillomania [TTM] [Figure 33-1] and pathological skin picking).

Figure 33-1 Left-side view of a trichotillomania patient’s scalp demonstrating areas of alopecia (balding) and hair thinning.

Approximately 2% to 3% of the world’s population will suffer from OCD at some point in their lives,³ and higher numbers will suffer from OCRDs. Most individuals with OCD spend an average of 17 years before they receive an appropriate diagnosis and treatment for their illness.⁴ Although these disorders have a waxing and waning course, they frequently increase in severity when left untreated, which causes unnecessary pain to those afflicted and to their families. Hence, an understanding of OCD and OCRDs by clinicians is imperative to reduce the gap between the onset of symptoms and the eventual diagnosis, and to promote implementation of appropriate strategies for long-term symptomatic relief. This chapter provides a general description of these conditions, followed by characterization of the epidemiology (including risk factors), the genetics, and the clinical features for OCD and OCRDs. Strategies for the clinical evaluation (including use of laboratory tests) and treatment of the illnesses are then discussed.

DEFINITIONS

OCD is listed as an anxiety disorder by the Diagnostic and Statistical Manual of Mental Disorders—Fourth Edition (DSM-IV).³ It is characterized by repetitive thoughts, images, impulses, or actions that are distressing, that are time-consuming, or that affect function. The condition is often kept a secret because of the shame associated with its peculiar symptoms. Symptoms experienced by OCD sufferers are diverse. Obsessions can focus on aggressive or sexually intrusive thoughts, religious scrupulosity, concerns about symmetry, hoarding, pathological doubt, or thoughts of contamination. Compulsions are also varied; they include washing, counting, checking, repeating, hoarding, ordering, and the conduct of mental rituals. More often than not, patients with OCD experience more than one type of symptom at any given time, and the symptoms change over the course of the illness.

OCRDs are characterized by the presence of repetitive or excessively compulsive behaviors, some of which are preceded by increased tension and followed by a sense of relief. What constitutes an “OCD spectrum” or “OCD-related” disorder remains controversial. At present, prominent researchers cannot agree on how broad the OCD spectrum should be.⁵ Thus, OCRDs discussed in this chapter are those that are most often considered in this category.

Body dysmorphic disorder (BDD) and hypochondriasis are classified by the DSM-IV as somatoform disorders, and are characterized by repetitive, excessive worries and behaviors related to a slight or imagined physical defect or illness. Trichotillomania and pathological skin picking are classified by the DSM-IV as impulse control disorders; in both conditions, affected individuals are unable to resist the urge to recurrently pull their hair or to pick their skin. Trichotillomania is the prototypical impulse control disorder that will be discussed in this chapter. Tic disorders (such as Tourette’s disorder) are characterized by recurrent stereotyped motor or phonic tics that are resisted on occasion in the short term, but not in the long term. All of these OCRDs are debilitating and distressing; they adversely affect the quality of a person’s life.

EPIDEMIOLOGY AND RISK FACTORS

CLINICALLY RELEVANT GENETICS

Numerous lines of evidence support the genetic basis for OCD and OCRDs. Twin and family aggregation studies of OCD report higher than expected rates of OCD in relatives.^47–50 This was confirmed in a meta-analysis of five OCD family studies that included 1,209 first-degree relatives,⁵¹ which calculated a significantly increased risk of OCD among relatives of probands (8.2%) versus controls (2.0%) (odds ratio [OR] = 4.0). However, in studies ascertained through children or adolescents, familial risk appears to be even higher (9.5% to 17%) than that for those with later-onset OCD.^52–58 In family studies by Nestadt, Pauls, and others, approx-imately half of the OCD cases have not proven to be familial.^59–61

Although twin studies can provide compelling evidence for the role of genetic factors in complex neuropsychiatric disorders, no large systematic twin studies have focused exclusively on OCD. Further, twin studies cannot provide conclusive evidence that unique genes are important for the manifestation of OCD. A recent review of OCD twin studies dating back to 1929 concluded that obsessive-compulsive symptoms are heritable, with genetic influences ranging from 45% to 65% in children and from 27% to 47% in adults.⁶²

Molecular genetic studies have begun to provide evidence that specific genes play a role in the manifestation of OCD. Segregation analyses have examined familial patterns of OCD transmission and noted the best fit for a dominant model in some studies.^61,63,64 However, results of combined segregation analyses suggest that OCD’s familial transmission is difficult to model. The most parsimonious solution suggests that there are at least some genes of major effect⁶⁵; it is highly likely that OCD is an oligogenic disorder with several genes that are important for the expression of the syndrome. At the present time, none of the four linkage studies for OCD or OCD symptoms reported genome-wide significance.^66–68 The following regions have been suggestive for susceptibility loci: 1q, 6q, 9p, 19q, 7p, and 15q.

OCD candidate genes have been studied based on their function and also their position in the genome. Serotonin-related genes considered in OCD include those coding for the serotonin transporter (5-HT_T)^69–71 and receptors (5-HT_2A,⁷² 5-HT_2B,⁷³ 5-HT_2C,⁷⁴ and 5-HT_1B),⁷⁰ as well as the serotonin enzyme (tryptophan hydroxylase).⁷⁵ Dopamine (DA)–related genes studied in OCD include DA transporter genes^76,77; D₂, D₃, and D₄ receptors⁷⁸; COMT⁷⁹; and MAO-A enzymes.^80,81 Glutamate-related genes reported to be associated with OCD include GRIK,^82,83 GRIN_2B,^83,84 and the glutamate transporter (SLC1A1).^85–87 Other genes that have been reported to be associated with OCD include the white-matter genes OLIG₂⁸⁸ and MOG.⁸⁹ Given the complexity of the OCD phenotype, it is unlikely that a single candidate gene will have a major impact on the disorder, and few if any genes have been consistently replicated in large samples.

With respect to genetic studies of OCRDs, Bienvenu and colleagues⁹⁰ explored familiality of these illnesses among the relatives of OCD probands and found significantly higher than expected rates of BDD (OR = 5.4), somatoform disorders (OR = 3.9), grooming disorders (OR = 1.8), and all spectrum disorders combined (OR = 2.7). Relatives of OCD probands have elevated rates of Tourette’s disorder and chronic tics (4.6%) versus relatives of controls (1%), regardless of a diagnosis of Tourette’s disorder in the probands.^49,91 This is especially true in families with earlier-onset OCD. Moreover, relatives of Tourette’s disorder probands have elevated rates of OCD as compared with controls.^92,93 It has also been suggested that TTM has an underlying genetic basis.^46,94,95 In the only twin study exploring the genetic basis for TTM, a significantly greater concordance rate was present among monozygotic (31.9%) than dizygotic (0%) twins for “clinically significant hair-pulling.”⁹⁶

PATHOPHYSIOLOGY

The pathophysiology of OCD is incompletely understood, although neurobiological models implicate dysfunction in several corticostriatal pathways.^97,98 OCD is considered to be a neuropsychiatric disorder, in part as it is associated with neurological conditions and movement disorders. In fact, OCD may develop following birth injury,⁹⁹ temporal lobe epilepsy,¹⁰⁰ or head injury.¹⁰¹

Neuroimaging findings indicate that OCD involves subtle structural and functional abnormalities of the orbitofrontal cortex, the anterior cingulate cortex, the caudate, the amygdala, and the thalamus (Figure 33-2).^{97,98,102–104} The nodes of the implicated frontocortical-basal ganglia-thalamocortical circuit are interconnected via two principal white-matter tracts—the cingulum bundle and the anterior limb of the internal capsule.

Figure 33-2 Positron emission tomographic omnibus subtraction images of provoked minus resting conditions for all subjects (N = 8; 13 scans per condition) displayed with a “hot iron” scale in units of z score, superimposed over a normal magnetic resonance image transformed to Talairach space, for the purpose of anatomical reference. All images are transverse sections parallel to the anterior commissure–posterior commissure plane, shown in conventional neuroimaging orientation (top = anterior, bottom = posterior, right = left, left = right). Each transverse section is labeled with its z coordinate, denoting its position with respect to the anterior commissure–posterior commissure line (superior > 0). Activation is found within regions of interest corresponding to a prior hypothesis. A, Orbitofrontal cortex bilaterally (P < 0.008); B and C, right caudate nucleus (P < 0.006); C, left thalamus (P = 0.07); and D, anterior cingulate cortex (P < 0.045). Other areas of substantial activation include (B) right putamen and (C) left and (D) right middle frontal cortex (not labeled).

(From Rauch SL, Jenike MA, Alpert NM, et al: Regional cerebral blood flow measured during symptom provocation in obsessive-compulsive disorder using oxygen 15–labeled carbon dioxide and positron emission tomography, Arch Gen Psychiatry 51:66, 1994.)

The basal ganglia are likely associated with abnormal compulsions of OCD. Damage to this region in both humans¹⁰⁵ and animal models¹⁰⁶ results in behaviors that resemble compulsions. Furthermore, diseases in humans that result from deterioration of basal ganglia (such as Huntington’s chorea and Parkinson’s disease) have increased rates of OCD.^107,108 Prefrontal and orbitofrontal regions are responsible for filtering information received by the brain and for suppressing unnecessary responses to external stimuli; these may be more associated with the obsessive symptoms of OCD.

There is also evidence of brain white-matter involvement in OCD. Patients with OCD have significantly more gray matter, less white matter, and abnormalities of white matter than do normal controls, which suggests a possible developmental etiological process.^109–111 Neurochemically, serotonergic¹¹² and glutamatergic systems have been implicated in OCD.

Other medical pathophysiological factors may be involved in the etiology of OCD. In rare cases, a brain insult (such as encephalitis, a striatal lesion [congenital or acquired], or head injury) directly precedes the development of OCD.¹¹² Research suggests that autoimmune processes, precipitated in some childhood-onset cases by beta-hemolytic streptococcal infection, may cause damage to striatal neurons in childhood-onset cases of OCD.^113–115

CLINICAL FEATURES AND DIAGNOSIS

The DSM-IV³ is currently used for the diagnosis of OCD and OCRDs (Table 33-1). The diagnosis of OCD requires the presence of either obsessions or compulsions. These must be significantly distressing, time-consuming, or interfering with the person’s normal routine, occupational function, social activities, or relationships with others. Figure 33-3 illustrates the living quarters of a patient with OCD and hoarding behavior.

Table 33-1 Diagnostic Criteria for Obsessive-Compulsive Disorder (DSM-IV)

DSM-IV, Diagnostic and Statistical Manual of Mental Disorders—Fourth Edition.³

Figure 33-3 Cluttered and overcrowded home of an OCD patient suffering with hoarding obsessions and compulsions.

Revisions from the DSM-III-R to the DSM-IV for OCD include the addition of mental compulsions, and exclusion, if the content of the obsessions or compulsions is restricted to another Axis I disorder (e.g., concern with appearance in the presence of BDD, or repeated hair-pulling with TTM) or if the obsessions or compulsions are due to the direct effects of a substance or general medical condition. A “poor insight type” may be specified if the person does not recognize the excessive or unreasonable nature of the obsessions and compulsions most of the time during the current episode. Figure 33-4 provides an image of a classic OCD symptom, handwashing.

Figure 33-4 OCD patient demonstrating a typical compulsive behavior of handwashing. Some patients may wash their hands hundreds of times daily, leading to inflamed, erythematous, and cracking skin.

It has been proposed that clinical features of the OCRDs may be categorized into three symptom clusters.¹¹⁶ These are a “somatic” cluster for BDD and hypochondriasis; a “reward deficiency” cluster for TTM and other impulse control disorders (such as Tourette’s disorder); and an “impulsivity” cluster for compulsive shopping, kleptomania, and intermittent explosive disorder. However, as previously noted, whether all of these disorders (especially the latter cluster) constitute OCRDs is an issue of ongoing debate.⁵

BDD is a disorder in which individuals suffer from a preoccupation with a slight or imagined defect in appearance that causes significant distress or impairment that is not strictly a manifestation of another disorder. Hypochondriasis involves a preoccupation with the inaccurate belief that one has, or is in danger of developing, a serious illness. This fear persists despite extensive evaluation and subsequent reassurance of good health by a medical professional. Tourette’s disorder is characterized by the presence of chronic motor and vocal tics, with symptoms manifesting before 18 years of age. These symptoms should persist for at least a year, with no 3-month symptom-free intervals.³ TTM involves repetitive hair-pulling that results in significant hair loss that is preceded by increasing tension, followed by relief or pleasure, and results in impaired function or significant distress.^117,118

EVALUATION, TESTS, AND LABORATORY FINDINGS

To assess an individual with a suspected OCD or OCRD, a systematic approach should be applied. Elements of a standard psychiatric assessment are included in the evaluation of an individual with suspected OCD or a suspected OCRD. This includes the assessment of the history of present illness, co-morbid symptoms, past psychiatric history, family psychiatric history, social and developmental history, review of systems, medical and substance history, medications and drug allergies, and the mental status examination.

Regarding the history of present illness, the duration and severity of symptoms and their precipitating, exacerbating, and ameliorating factors should be elucidated. Functional consequences of these symptoms in home, work, and social environments and the level of insight, resistance, and control over symptoms should also be assessed. Family insight and accommodation of symptoms (which permits their perpetuation) are other important factors to be determined. The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and checklist should be used to record the severity and lifetime presence of specific symptoms. There is also a children’s version of this scale, the Children’s Yale-Brown Obsessive Compulsive Scale (CY-BOCS). Alternatively, the Obsessive-Compulsive Inventory¹¹⁹ or the Obsessive-Compulsive Checklist¹²⁰ may be used.

Following the initial assessment, co-morbid illnesses or other more responsible disorders should be ruled out. (Figure 33-5 shows an algorithm for creation of a differential diagnosis.) For individuals with OCD, co-morbid OCRDs should be assessed, and vice versa. Tics and eating disorders¹²¹ may be more common in individuals with OCD. Clinical measures used to record OCRDs include the Yale Global Tic Severity Scale (YGTSS) for tics and Tourette’s disorder, the Massachusetts General Hospital (MGH) Hairpulling Scale for TTM,¹²² and the Body Dysmorphic Disorder Questionnaire for BDD.¹²³ Other conditions that should be assessed include depression and the risk of suicide. Other co-morbidities that occur at higher than expected rates include bipolar disorder,¹²⁴ personality disorders, and anxiety disorders (such as panic disorder, social phobia, or generalized anxiety disorder).^125,126 Further diagnoses (including ADHD and substance use disorders) should also be screened.

Figure 33-5 Algorithmic approach to establishing DSM-IV diagnoses of OCD and OCD-related disorders.

In the assessment of past psychiatric history, the duration of time at the maximum dosage of every past medication trial should be recorded. The length and success of past behavior or cognitive therapies and other psychotherapies also needs to be established. Careful attention should be paid to determine whether actual exposure and response prevention or cognitive therapy forms of cognitive-behavioral therapy (CBT) were received or if, alternatively, this was a form of supportive therapy that has not been reported as efficacious for OCD. Other factors that may affect the treatment include a history of substance abuse, which may impede compliance. Past mood instability may indicate the risk for a switch toward mania with administration of serotonergic agents. Panic attacks should stimulate use of caution with dosage increases, because these may trigger further attacks.

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