Symptom dimensions in obsessive-compulsive disorder
Date
2005-12
Authors
Lochner, Christine
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Background: Obsessive-compulsive disorder (OCD) is a neuropsychiatric condition
characterized by significant heterogeneity. It has been suggested that classification of OCD
into more homogeneous subtypes, and identification of their associations with etiological
factors (e.g. genetic variants, or psychological trauma), and outcome (e.g. disability and
treatment response), may be useful. The identified subtypes are not definitive yet and
continue to be subject to revision. The overall objective of this dissertation was to assess
comprehensively a sample of OCD patients, and to use cluster analytic methods to delineate
valid OCD subtypes.
Methods: Patients meeting DSM-IV criteria for a primary diagnosis of OCD (N=261) on the
Structured Clinical Interview for Axis I Disorders - Patient Version (SCID-I/P), with ages
ranging from 16 to 71, took part in the study. The newly developed Structured Clinical
Interview for the Diagnosis of putative Obsessive-Compulsive Spectrum Disorders (SCIDOCSD)
was administered to assess OCD-related conditions not covered by the SCID-I/P.
OCD subtyping, based on OCD symptomatology (assessed with the Yale-Brown Obsessive-
Compulsive Symptom Checklist [YBOCS-CL]), and based on comorbidity with the OCD
spectrum of disorders (assessed with the SCID-OCSD), proceeded along the following lines:
Firstly, latent class cluster analysis (LCA), a categorical analogue to traditional factor
analysis (FA), and with many advantages compared to FA, was implemented with the (nine)
most frequently endorsed OC symptoms. Secondly, in an attempt to remedy some of the
limitations of the LCA (e.g. increased potential for computational instability when additional
indicators / symptoms were included), cluster analyses (Ward’s method) were performed on
all of the items of the YBOCS-CL and SCID-OCSD, respectively, for all OCD patients. The
associations of cluster scores with demographic variables (age, gender), clinical variables
(age of onset, obsessive-compulsive symptom severity and dimensions, level of insight,
temperament, childhood trauma, treatment response) and genotypes were then examined, using Spearman correlation coefficients, one-way analysis of variance (ANOVA), and Mann-
Whitney U-tests, where appropriate.
Results: The findings suggested that increased presentation of symptoms characteristic of
each of the clusters of cases was associated with specific demographic and clinical
characteristics, which substantiated the presence of distinct clinical subtypes of OCD.
Cluster analysis of the 45 selected items of the YBOCS-CL in this sample of OCD patients
identified 6 separate clusters; these clusters were labelled “Contamination fears / washing”,
“Hoarding / collecting”, “Symmetry / ordering / counting / arranging / repeating”, “Sexual”,
“Somatic, religious and diverse” and “Harm-related”. Increased presentation of symptoms
characteristic of each of the clusters was associated with specific demographic, clinical and,
in some cases, genetic characteristics. Of note, the findings indicated the L/L (met/met)
genotype of COMT Val158Met polymorphism plays a major role in the increased
manifestation of sexual, somatic, religious and diverse, and harm-related symptoms of OCD,
as such contributing to the relatively limited data on OC symptom subtypes and genetics.
However, the fact that the associated features did not clearly and uniquely differentiate
clusters and that clusters were significantly correlated with one another suggested that the
delineation of the OCD complex into OC symptom clusters is not the only way to approach
the heterogeneity characteristic of OCD. Nevertheless, the significant comorbidity with
OCSD’s in the identified clusters (e.g. tics associated with sexual obsessions / compulsions)
highlighted the significant relationship of OCD with the OCSD’s. This again raised the
question about the way in which the OCSD’s “fit” with the standard OC symptomatology
outlined in the YBOCS-CL. A cluster analysis of OCSD’s in OCD patients identified a
Tourette’s syndrome / tics subtype of OCD (part of the so-called “reward deficiency” cluster),
as well as an impulsivity subtype, and a somatic subtype – each associated with specific
clinical and demographic variables. Here, a significant relationship between the identified clusters and the investigated dopaminergic and serotonergic polymorphisms was not found,
suggesting that variants in other genes in these systems should also be explored.
Conclusion: The main finding was that OCD is indeed a heterogeneous disorder that may
be subtyped into different symptom dimensions. The identified OCD subtypes with their
associated features were to a large extent consistent with previously published data.
However, in contrast to factor analysis, LCA provided a novel, appropriate and
advantageous statistical analysis strategy for the data. Furthermore, to our knowledge, the
attempt to classifiy OCD according to comorbid OCSD’s was the first cluster analysis based
on a prospective comprehensive interview investigating a range of OCSD’s. As such,
although the dimensional structure of OCD is still not entirely understood, the categorization
of our OCD patients into different groups and the investigation of their respective features
have gone beyond the literature and thus add another dimension to the increasing efforts to
fully delineate OCD subtypes.
Description
Thesis (PhD (Psychiatry))--University of Stellenbsoch, 2005.
Keywords
Obsessive-compulsive disorder, Dissertations -- Psychiatry, Theses -- Psychiatry