Cluster analysis of obsessive-compulsive spectrum disorders in patients with obsessive-compulsive disorder: clinical and genetic correlates
Introduction
There is growing recognition that obsessive-compulsive disorder (OCD) is a heterogeneous disorder, with clinical subtypes that are characterized by differing pathophysiological mechanisms and treatment outcomes [1], [2]. In clinical practice, for example, only about 40% to 60% of patients respond to the first trial of any particular selective serotonin reuptake inhibitor (SSRI) [3]. Other neurotransmitter mechanisms may also be involved in OCD; dysregulation of the dopaminergic system, in particular, has been postulated as a crucial factor in treatment-resistant OCD [4], [5]. Interestingly, the dopaminergic system may also be sensitized by repeated stress exposure [6], [7]. Furthermore, it has been suggested that patients with OCD who have particular variants of genes of the dopamine system are more likely to have tics [5], [8], and the presence of tics predicts worse response to SSRIs [8], [9]. A better understanding of subtypes of OCD might ultimately lead to new and more effective treatments [2].
One approach to subtyping OCD may be to consider issues of comorbidity. For instance, in their attempt to characterize psychopathological classes of disorders related to OCD to distinguish more homogeneous phenotypes with distinct etiologies, Nestadt et al [10] suggested that the OCD phenotype is expressed in 2 different subgroups on the basis of the presence of additional clinical syndromes that frequently accompany the condition. Moreover, OCD is commonly comorbid with obsessive-compulsive spectrum disorders (OCSDs; ie, conditions that share phenomenological and neurobiological features with OCD). For example, patients with comorbid OCD and Tourette's disorder (TD) appear to be characterized by specific demographic features (they are more likely to be male) and clinical characteristics (they are less likely to respond to SSRIs) [9]. While most patients with OCD suffer from at least one comorbid OCD spectrum disorder [11], there has been relatively little systematic investigation of the structure and implications of such comorbidity. It is possible, however, that different dimensions of OCD spectrum comorbidity in OCD correspond to differential involvement of various neurochemical systems and neuroanatomical circuits [12].
In this study, we aimed to delineate the hypothesized spectrum of OCD-related disorders in OCD using cluster analysis. The association of identified clusters with demographic variables (age, gender), clinical variables (age of onset, obsessive-compulsive [OC] symptom severity and dimensions, level of insight, temperament/character, treatment response), and monoaminergic genotypes was examined.
Section snippets
Subjects
Two hundred and ten adult patients with OCD (N = 210, 102 men and 108 women), with ages ranging between 18 and 75 years (35.7 ± 13.3), took part in the study. To be eligible, patients had to meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) [13] criteria for a primary diagnosis of OCD on the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis I Disorders–Patient Version (SCID-II/P) [14] and had to
Cluster analysis
At the 1.1 linkage distance level, the following 3 clusters were obtained (Fig. 1):
- (1)
Cluster I, subsequently named “reward deficiency,” included TTM, pathological gambling, hypersexual disorder, and TD.
- (2)
Cluster II, subsequently named “impulsivity,” included compulsive shopping, kleptomania, eating disorders (including anorexia and bulimia nervosa), self-injury, and IED.
- (3)
Cluster III, subsequently named “somatic,” included BDD and hypochondriasis.
Comparison data
The following significant results were found:
- (1)
Cluster I
Discussion
Cluster analysis of the OCSDs in our sample of patients with OCD identified 3 separate clusters at the 1.1 linkage distance level. We labeled these clusters as (1) “reward deficiency” (including TTM, pathological gambling, hypersexual disorder, and TD), (2) “impulsivity” (including compulsive shopping, kleptomania, eating disorders, self-injury, and IED), and (3) “somatic” (including BDD and hypochondriasis).
A substantial literature has documented the comorbidity between OCD and TD, and the
Acknowledgments
This work was supported by the Medical Research Council of South Africa, the National Research Fund, and by a grant from the Obsessive-Compulsive Foundation. The help of the Obsessive-Compulsive Association of South Africa is gratefully acknowledged.
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2017, Asian Journal of PsychiatryCitation Excerpt :Further validation of results by subgroup characteristics related to treatment response or the etiology of OCD showed greater support for a seven subgroup taxonomy (Calamari et al., 2004). Another study clustered OCD patients into 3 clusters based on their comorbidity of obsessive-compulsive spectrum disorders (OSCDs) using Ward’s method (Lochner et al., 2005). Cluster analysis of 45 items of YBOCS-CL reported by this sample identified six-cluster solution (Lochner et al., 2008).