- Email: [email protected]
Lumping versus splitting: A commentary on subtyping in OCD
LumpingVersus Splitting: A Commentary on Subtyping in OCD David A. Clark, University of New Brunswick
This commentary discusses a number of pertinent concerns that were raised in this special series on subtyping in
obsessive-compulsive disorders (OCD). The central question addressed in the three articles in the series is whether a better subtype classification of OCD could be developed if it is based on type of faulty cognition as well as symptom presentation. It is concluded that a more cognitive approach to OCD subtyping may not address many of the problems inherent in subtype research, nor will the development of special manualized treatment protocols for OCD subtypes necessarily yield significant improvements in treatment effectiveness. An alternative to OCD subtyping based on a categorical perspective is some form of profiling that recognizes the dimensional nature of OCD symptom and cognition variables.
C L I N I C A L RESEARCHERS HAVE frequently c o m m e n t e d on the diverse and heterogeneous clinical
presentation found in obsessive-compulsive disorder (OCD). The apparent heterogeneity of OCD is somewhat unique among the anxiety disorders, which has led to special challenges in delineating the diagnostic boundaries of the disorder. Even at the most basic diagnostic level, not all researchers agree that OCD belongs with the anxiety disorders, arguing instead that it is also related to other major classes of psychopathology such as mood, personality, eating, tic, impulse control, or schizophrenic disorders (see Brown, 1998). In addition to this diagnostic conundrum, a diverse clinical presentation means that attempts to build an all-encompassing etiological model of the disorder, or to develop a robust treatment protocol, frequently fail to be equally applicable to all manifestations of OCD. Even if we take a core symptom of OCD, such as the subjective feeling of anxiety or distress associated with obsessional thinking, it is now clear that anxiety is not universally experienced in OCD. For example, individuals with obAddress correspondence to D. A. Clark, Department of Psychology, University of New Brunswick, Bag Service #45444, Fredericton, New Brunswick, E3B 6E4, Canada; e-mail: [email protected]. BEHAVIORTHERAPY36, 401--404, 2005 005-7894/05/401~'0451.00/0
Copyright2005 by Associationfor Advancementof BehaviorTherapy All rights for reproductionin any formreserved.
sessional concerns about symmetry and precision may be more motivated to achieve a "just right" perception rather than reduce or eliminate anxiety (Leckman, Walker, Goodman, Pauls, & Cohen, 1994; Summerfeldt, Richter, Antony, & Swinson, 1999; but see Radomsky & Rachman, 2004, for a contrary view). If a single phenomenologic feature cannot be found that defines OCD as a unitary diagnostic entity, then it is reasonable to ask whether the disorder is more accurately conceptualized as a spectrum of disorders involving more homogeneous subgroups. Rather than focus on a single theory or treatment approach, researchers would formulate models and interventions that would be applicable only to a particular subtype of OCD. Thus the subtyping question is a fundamental issue that strikes at the heart of our understanding and treatment of OCD. Past and present theories, research and treatment of OCD have generally assumed a unitary diagnostic perspective. However, if the "splitters" are correct, then our research and clinical focus has been wrong and we should redirect our efforts to particular subtypes of OCD. In some sense this movement toward a subtype perspective is already apparent in the recent cognitive-behavioral theories offered for compulsive checking (Rachman, 2002), hoarding (Frost & Steketee, 1998), and compulsive washing (Jones & Menzies, 1998). This special section of Behavior Therapy on subtyping, then, addresses an important topic that has a significant impact on how we research and treat OCD. The papers in this series consider whether our attempts to identify reliable and valid OCD subtypes might be improved by taking into consideration the cognitive basis of the disorder. To date, subtyping studies based on clinical observation or more empirically based statistical approaches have focused exclusively on the frequency and content of obsessions and compulsions. Radomsky and Taylor (2005) discuss a number of conceptual and methodological challenges that face research on OCD subtypes. Haslam, Williams, Kyrios, McKay, and Taylor (2005) present a taxometric analysis of OCD based on self-reported symptom presentation versus specific OC-relevant beliefs. Sookman, Abramowitz, Calamari, Wilhelm, and McKay (2005) discuss whether treatment efficacy can be improved by selectively tailoring our interventions
402
CLARK
to OCD subtypes. In this commentary I would like to focus on three issues that are more or less addressed in these articles: Why have symptom-based subtypes not provided an adequate subclassification of OCD? Will the inclusion of cognitive variables improve our subtyping efforts? And third, how promising is targeted intervention for OCD subtypes? The Problem With Symptom-Based Subtypes The splitting of OCD into a variety of subtypes has been spurred on by clinical observation that there may be a limited number of OC symptom types, such as contamination obsessions, doubting and checking compulsions, sexual and aggression obsessions, somatic obsessions, hoarding, need for symmetry and precision, and religious obsessions (Rasmussen & Eisen, 1998). The identification of OCD subgroups based on clinical observation of prominent symptom features has led to fruitful research on distinguishing phenomenology, underlying psychological mechanisms and treatment of compulsive washing and checking (e.g., Rachman & Hodgson, 1980) and, to a lesser extent, obsessional rumination without overt compulsions (e.g., Freeston et al., 1997). This clinical approach to subtyping, however, is neither systematic nor reliable. More empirically based research has appeared in recent years involving cluster analysis of symptom checklists like the Yale-Brown Obsessive-Compulsive Inventory (YBOCS). Initially, Leckman et al. (1997) factor analyzed 13 rationally determined symptom categories of the 64-item YBOCS to yield four components: obsessions and checking, symmetry and ordering, cleanliness and washing, and hoarding. This factor structure, though similar, was not entirely replicated in subsequent studies, especially at the item level (Mataix-Cols, Rauch, Manzo, Jenike, & Baer, 1999; Summerfeldt et al., 1999). Cluster analysis of the rationally determined YBOCS symptom checklist resulted in five different subgroups: harming obsessions and checking compulsions, hoarding, contamination obsessions and washing compulsions, certainty, and miscellaneous obsessions (Calamari, Wiegartz, & Janeck, 1999). In an attempted replication of the cluster analysis on a second OCD sample, Calamari et al. (2004) failed to find a hoarding subgroup, and a separate symmetry subgroup emerged in the solution (see also some differences in the cluster analysis by Abramowitz, Franklin, Schwartz, & Furr, 2003). Across studies, then, contamination/washing has emerged most reliably, whereas hoarding, harming/ checking, and symmetry subtypes have shown less consistency.
Radomsky and Taylor (2005) suggest a number of reasons why current OCD symptom-based subtype research might not produce the most reliable or valid results. They begin by noting that a number of domains of investigation should be employed in the search for subtypes. Progress in OCD subtype research has probably been hampered by overreliance on self-report or interview-based clinical descriptive data. As well, symptom-based subtype research is limited by the psychometric characteristics of the measurement tools. Content validity is a particularly important issue in subtype research. If a symptom measure overrepresents certain obsessive and compulsive symptom content but underrepresents or even omits other content, then the subtyping profile that emerges will be biased. Radomsky and Taylor note that subtyping based on constructs that are applicable to other disorders as well as OCD will present particular conceptual challenges. The problems of allocating individuals to particular OCD subtypes become especially difficult unless the function of the obsession or compulsion is taken into account. How would we categorize an obsession involving repugnant sexual acts in someone who responds by repetitively reciting confessional prayers? Is this a religious or sexual obsession? Even if we classify the individual on a functional basis (i.e., classify it as a religious obsession if the threat involves fear of God's punishment but a sexual obsession if the threat is concern that one will act on the obsession), Radomsky and Taylor remind us that in actual OCD cases obsessions and compulsions often serve mixed functions. Can the inclusion of cognitive variables provide further insights into the function of obsessive and compulsive symptoms thereby offering a stronger conceptual framework for defining OCD subtypes? At this point it is unclear whether there will be substantial progress in developing a solid OCD subtype classification based on cognitive-behavioral considerations. The OC-relevant beliefs and appraisals identified by the Obsessive Compulsive Cognitions Working Group (1997), for example, are highly intercorrelated and most are not specific to OCD. Our measures of these constructs are still in an initial stage of development. On the other hand, if a more contextualized and functional analysis of obsessive and compulsive symptoms is needed in order to develop a truly valid OCD subtype classification, then the assessment of faulty appraisals and beliefs could play an integral role in this enterprise.
A Cognitive Approach to OCD Subtypes If distinct diagnostic subtypes exist within OCD, then we might expect certain symptoms or cognitive phenomena to manifest categorical rather than di-
COMMENTARY:
LUMPING
mensional characteristics. Haslam et al. (2005) present the first taxometric analysis of OCD cognition and symptom variables. Employing a large OCD sample, they investigated whether contamination, checking, and obsessionality symptom-based subtypes might occur in responses to the Padua Inventory (PI) and whether responsibility/threat estimation, perfectionism/intolerance of uncertainty, and importance/control of thoughts cognition-based subtypes could be derived from the Obsessive Beliefs Questionnaire (OBQ). Evidence for the categorical nature of these variables was not overwhelming. Contamination, responsibility/threat, and perfectionism/intolerance of uncertainty exhibited strong and consistent dimensionality. Results for checking and pure obsessionality were less consistent, with some weak indication that discrete latent subclasses exist. The strongest evidence for a taxonic model was found for importance/control of thoughts, yet even here the findings were not entirely consistent. Overall, though, support for dimensionality was much stronger than for the existence of categorical symptom or cognition variables in OCD. The findings from this study have direct implications on the subtype issue in OCD. If OCD cognition and symptom variables are primarily dimensional in nature, then it will be much harder to form meaningful discrete subtypes of the disorder. The alternative might be the development of some form of profile analysis where individuals with OCD vary along primary symptom and cognition dimensions. At this stage it would be premature to abandon categorical research of OCD simply on the basis of the somewhat discouraging findings from initial taxometric analysis.
Treatment of OCD Subtypes The final article in this series by Sookman et al. (2005) discusses treatment implications of adopting a subtype classification of OCD. The authors state that standard exposure and response prevention (ERP) outcome studies regard OCD as a homogeneous group, which obscures whether different symptom subtypes vary in their treatment response. Their review of ERP outcome studies suggests that certain subtypes, such as obsessional rumination without overt compulsion and individuals with hoarding compulsions, may not respond as well to treatment. Sookman et al. suggest that a shift toward a more cognitive orientation in treatment might improve efficacy, especially for patients with checking or hoarding compulsions, or those with obsessions and no overt compulsions. Two cognitive-behavior therapy (CBT) studies are presented in which specific beliefs and appraisals for different OCD subtypes were targeted for change.
VS.
SPLITTING
403
Sookman et al. conclude that CBT for OCD could be improved by developing manualized treatment for OCD subtypes that target faulty beliefs and appraisals that characterize each subtype. Although the call for more research on the treatment of OCD subtypes is important, I am not sure the "pay-off" in terms of enhanced interventions will be as significant as expected. First, the ERP and CBT interventions developed for OCD more generally have proven quite adaptable and robust to more specific manifestations of the disorder. For example, Abramowitz et al. (2003) found that ERP was equally effective in treating the harming obsession, contamination, unacceptable thoughts and symmetry subtypes (based on a cluster analysis of the YBOCS checklist) but not the hoarding cluster. In addition, some of the studies reviewed by Sookman et al. (2005) indicate that ERP-based treatment can be effective for subtypes like obsessional ruminators. Based on the empirical data, it is not clear that the development of specialized CBT for OCD subtypes would improve treatment outcome, with the possible exception of hoarding. Second, Sookman et al. (2005) advocate an idiographic approach to the treatment of OCD subtypes. But is this not what we already do when we develop a case formulation as part of CBT for OCD (see Clark, 2004)? Subsequent cognitive and ERP strategies are then tailored to the unique symptom presentation and cognitive profile of the patient. I am not sure that manualized treatments for specific OCD subtypes will lead to better interventions unless CBT practitioners have abandoned case conceptualization and failed to tailor their interventions to the unique characteristics of individual clients. Finally, the high correlations among OC belief domains cast further doubt on whether specialized treatment approaches for specific cognitive or symptom presentations is a viable option. Instead of viewing inflated responsibility, overestimated threat, importance and control of thoughts, or perfectionism and intolerance of uncertainty as distinct appraisal and belief domains, it is more precise to view them as overlapping constructs that capture a slightly different perspective on how individuals endow unwanted intrusive thoughts and obsessions with meaning and personal significance. Conclusion The search for reliable subtypes of OCD addresses a fundamental question about the nature of this disorder. The articles in this special series raise the possibility that a greater focus on the faulty appraisals and beliefs that have been identified as pathognomonic in OCD might yield more precise and reliable OCD subtypes. In this commentary I
404
CLARK
have suggested a number of reasons why the inclusion of cognitive variables may not address the problems evident when subtyping is based entirely on symptom content. Naturally, it would be premature to abandon subtype research in OCD because our work on this issue is still in its infancy. On the other hand, it would also be naYve to assume that research and treatment of OCD subtypes will automatically advance our understanding and response to OCD. Some form of profiling based on symptom and cognition dimensions may be the better alternative for OCD research and treatment. In the meantime we must await further research to judge the merits of subtyping in OCD. References Abramowitz, J. S., Franklin, M. E., Schwartz, S. A., & Furr, J. M. (2003). Symptom presentation and outcome of cognitivebehavioral therapy for obsessive-compulsive disorder. Journal of Consulting and Clinical Psychology, 71, 1049 - 1057. Brown, T. A. (1998). The relationship between obsessivecompulsive disorder and other anxiety-based disorders. In R. P. Swinson, M. M. Antony, S. Rachman, & M. A. Richter (Eds.), Obsessive-compulsive disorder: Theory, research and treatment (pp. 207-226). New York: Guilford Press. Calamari, J. E., Wiegartz, P. S., & Janeck, A. S. (1999). Obsessive-compulsive disorder subgroups: A symptom-based clustering approach. Behaviour Research and Therapy, 37, 113-125. Calamari, J. E., Wiegartz, P. S., Riemann, B. C., Cohen, R. J., Greer, A., Jacobi, D. M., Jahn, S. C., & Carmin, C. (2004). Obsessive-compulsive disorder subtypes: An attempted replication and extension of a symptom-based taxonomy. Behaviour Research and Therapy, 42, 647-670. Clark, D. A. (2004). Cognitive-behavioral therapy for OCD. New York: Guilford Press. Freeston, M. H., Ladouceur, R., Gagnon, E, Thibodeau, N., Rheame, J., Letarte, H., & Bujold, A. (1997). Cognitivebehavioral treatment of obsessive thoughts: A controlled study. Journal of Consulting and Clinical Psychology, 65, 405-413. Frost, R. O., & Steketee, G. (1998). Hoarding: Clinical aspects and treatment strategies. In M. A. Jenike, L. Baer, & W. E. Minichiello (Eds.), Obsessive-compulsive disorder: Practical management (3rd ed., pp. 533-554). St. Louis: Mosby Press. Haslam, N., Williams, B. J., Kyrios, M., McKay, D., & Taylor,
S. (2005). Subtyping obsessive-compulsive disorder: A taxometric analysis. Behavior Therapy, 36, 381-391. Jones, M. K., & Menzies, R. G. (1998). Danger ideation reduction therapy (DIRT) for obsessive-compulsive washers: A controlled trial. Behaviour Research and Therapy, 36, 959970. Leckman, J. E, Grice, D. E., Boardman, J., Zhang, H., Vitale, A., Bondi, C., Alsobrook, J., Peterson, B. S., Cohen, D. J., Rasmussen, S. A., Goodman, W. K., McDougle, C. J., & Pauls, D. L. (1997). Symptoms of obsessive-compulsive disorder. American Journal of Psychiatry, 154, 911-917. Leckman, J. E, Walker, D. E., Goodman, W. K., Pauls, D. L., & Cohen, D. J. (1994). "Just right" perceptions associated with compulsive behavior in Tourette's syndrome. American Journal of Psychiatry, 151,675-680. Mataix-Cols, D., Rauch, S. L., Manzo, P. A., Jenike, M. A., & Baer, L. (1999). Use of factor-analyzed symptom dimensions to predict outcome with serotonin reuptake inhibitors and placebo in the treatment of obsessive-compulsive disorder. American Journal of Psychiatry, 156, 1409-1416. Obsessive Compulsive Cognitions Working Group. (1997). Cognitive assessment of obsessive-compulsive disorder. Behaviour Research and Therapy, 35, 667-681. Rachman, S. J. (2002). A cognitive theory of compulsive checking. Behaviour Research and Therapy, 40, 625-639. Rachman, S. J., & Hodgson, R. J. (1980). Obsessions and compulsions. Englewood Cliffs, NJ: Prentice-Hall. Radomsky, A. S., & Rachman, S. (2004). Symmetry, ordering and arranging compulsive behaviour. Behaviour Research and Therapy, 42, 893-913. Radomsky, A. S., & Taylor, S. (2005). Subtyping OCD: Prospects and problems. Behavior Therapy, 36, 371-379. Rasmussen, S. A., & Eisen, J. L. (1998). The epidemiology and clinical features of obsessive-compulsive disorder. In M. A. Jenike & W. E. Minichiello (Eds.), Obsessive-compulsive disorders: Practical management (pp. 12-43). St. Louis: Mosby. Sookman, D., Abramowitz, J. S., Calamari, J. E., Wilhelm, S., & McKay, D. (2005). Subtypes of obsessive-compulsive disorder: Implications for specialized cognitive behavior therapy. Behavior Therapy, 36, 393-400. Summerfeldt, L. J., Richter, M. A., Antony, M. M., & Swinson, R. P. (1999). Symptom structure in obsessive-compulsive disorder: A confirmatory factor-analytic study. Behaviour Research and Therapy, 37, 297-311. Taylor, S., Abramowitz, J. S., McKay, D., Calamari, J. E., Sookman, D., Kyrios, M., Wilhelm, S., & Carmin, C. (2005). Do dysfunctional beliefs play a role in all types of obsessive-compulsive disorder? Journal of Anxiety Disorders. RECEIVED: December 22, 2004
ACCEPTED: February 1, 2005
This commentary discusses a number of pertinent concerns that were raised in this special series on subtyping in
obsessive-compulsive disorders (OCD). The central question addressed in the three articles in the series is whether a better subtype classification of OCD could be developed if it is based on type of faulty cognition as well as symptom presentation. It is concluded that a more cognitive approach to OCD subtyping may not address many of the problems inherent in subtype research, nor will the development of special manualized treatment protocols for OCD subtypes necessarily yield significant improvements in treatment effectiveness. An alternative to OCD subtyping based on a categorical perspective is some form of profiling that recognizes the dimensional nature of OCD symptom and cognition variables.
C L I N I C A L RESEARCHERS HAVE frequently c o m m e n t e d on the diverse and heterogeneous clinical
presentation found in obsessive-compulsive disorder (OCD). The apparent heterogeneity of OCD is somewhat unique among the anxiety disorders, which has led to special challenges in delineating the diagnostic boundaries of the disorder. Even at the most basic diagnostic level, not all researchers agree that OCD belongs with the anxiety disorders, arguing instead that it is also related to other major classes of psychopathology such as mood, personality, eating, tic, impulse control, or schizophrenic disorders (see Brown, 1998). In addition to this diagnostic conundrum, a diverse clinical presentation means that attempts to build an all-encompassing etiological model of the disorder, or to develop a robust treatment protocol, frequently fail to be equally applicable to all manifestations of OCD. Even if we take a core symptom of OCD, such as the subjective feeling of anxiety or distress associated with obsessional thinking, it is now clear that anxiety is not universally experienced in OCD. For example, individuals with obAddress correspondence to D. A. Clark, Department of Psychology, University of New Brunswick, Bag Service #45444, Fredericton, New Brunswick, E3B 6E4, Canada; e-mail: [email protected]. BEHAVIORTHERAPY36, 401--404, 2005 005-7894/05/401~'0451.00/0
Copyright2005 by Associationfor Advancementof BehaviorTherapy All rights for reproductionin any formreserved.
sessional concerns about symmetry and precision may be more motivated to achieve a "just right" perception rather than reduce or eliminate anxiety (Leckman, Walker, Goodman, Pauls, & Cohen, 1994; Summerfeldt, Richter, Antony, & Swinson, 1999; but see Radomsky & Rachman, 2004, for a contrary view). If a single phenomenologic feature cannot be found that defines OCD as a unitary diagnostic entity, then it is reasonable to ask whether the disorder is more accurately conceptualized as a spectrum of disorders involving more homogeneous subgroups. Rather than focus on a single theory or treatment approach, researchers would formulate models and interventions that would be applicable only to a particular subtype of OCD. Thus the subtyping question is a fundamental issue that strikes at the heart of our understanding and treatment of OCD. Past and present theories, research and treatment of OCD have generally assumed a unitary diagnostic perspective. However, if the "splitters" are correct, then our research and clinical focus has been wrong and we should redirect our efforts to particular subtypes of OCD. In some sense this movement toward a subtype perspective is already apparent in the recent cognitive-behavioral theories offered for compulsive checking (Rachman, 2002), hoarding (Frost & Steketee, 1998), and compulsive washing (Jones & Menzies, 1998). This special section of Behavior Therapy on subtyping, then, addresses an important topic that has a significant impact on how we research and treat OCD. The papers in this series consider whether our attempts to identify reliable and valid OCD subtypes might be improved by taking into consideration the cognitive basis of the disorder. To date, subtyping studies based on clinical observation or more empirically based statistical approaches have focused exclusively on the frequency and content of obsessions and compulsions. Radomsky and Taylor (2005) discuss a number of conceptual and methodological challenges that face research on OCD subtypes. Haslam, Williams, Kyrios, McKay, and Taylor (2005) present a taxometric analysis of OCD based on self-reported symptom presentation versus specific OC-relevant beliefs. Sookman, Abramowitz, Calamari, Wilhelm, and McKay (2005) discuss whether treatment efficacy can be improved by selectively tailoring our interventions
402
CLARK
to OCD subtypes. In this commentary I would like to focus on three issues that are more or less addressed in these articles: Why have symptom-based subtypes not provided an adequate subclassification of OCD? Will the inclusion of cognitive variables improve our subtyping efforts? And third, how promising is targeted intervention for OCD subtypes? The Problem With Symptom-Based Subtypes The splitting of OCD into a variety of subtypes has been spurred on by clinical observation that there may be a limited number of OC symptom types, such as contamination obsessions, doubting and checking compulsions, sexual and aggression obsessions, somatic obsessions, hoarding, need for symmetry and precision, and religious obsessions (Rasmussen & Eisen, 1998). The identification of OCD subgroups based on clinical observation of prominent symptom features has led to fruitful research on distinguishing phenomenology, underlying psychological mechanisms and treatment of compulsive washing and checking (e.g., Rachman & Hodgson, 1980) and, to a lesser extent, obsessional rumination without overt compulsions (e.g., Freeston et al., 1997). This clinical approach to subtyping, however, is neither systematic nor reliable. More empirically based research has appeared in recent years involving cluster analysis of symptom checklists like the Yale-Brown Obsessive-Compulsive Inventory (YBOCS). Initially, Leckman et al. (1997) factor analyzed 13 rationally determined symptom categories of the 64-item YBOCS to yield four components: obsessions and checking, symmetry and ordering, cleanliness and washing, and hoarding. This factor structure, though similar, was not entirely replicated in subsequent studies, especially at the item level (Mataix-Cols, Rauch, Manzo, Jenike, & Baer, 1999; Summerfeldt et al., 1999). Cluster analysis of the rationally determined YBOCS symptom checklist resulted in five different subgroups: harming obsessions and checking compulsions, hoarding, contamination obsessions and washing compulsions, certainty, and miscellaneous obsessions (Calamari, Wiegartz, & Janeck, 1999). In an attempted replication of the cluster analysis on a second OCD sample, Calamari et al. (2004) failed to find a hoarding subgroup, and a separate symmetry subgroup emerged in the solution (see also some differences in the cluster analysis by Abramowitz, Franklin, Schwartz, & Furr, 2003). Across studies, then, contamination/washing has emerged most reliably, whereas hoarding, harming/ checking, and symmetry subtypes have shown less consistency.
Radomsky and Taylor (2005) suggest a number of reasons why current OCD symptom-based subtype research might not produce the most reliable or valid results. They begin by noting that a number of domains of investigation should be employed in the search for subtypes. Progress in OCD subtype research has probably been hampered by overreliance on self-report or interview-based clinical descriptive data. As well, symptom-based subtype research is limited by the psychometric characteristics of the measurement tools. Content validity is a particularly important issue in subtype research. If a symptom measure overrepresents certain obsessive and compulsive symptom content but underrepresents or even omits other content, then the subtyping profile that emerges will be biased. Radomsky and Taylor note that subtyping based on constructs that are applicable to other disorders as well as OCD will present particular conceptual challenges. The problems of allocating individuals to particular OCD subtypes become especially difficult unless the function of the obsession or compulsion is taken into account. How would we categorize an obsession involving repugnant sexual acts in someone who responds by repetitively reciting confessional prayers? Is this a religious or sexual obsession? Even if we classify the individual on a functional basis (i.e., classify it as a religious obsession if the threat involves fear of God's punishment but a sexual obsession if the threat is concern that one will act on the obsession), Radomsky and Taylor remind us that in actual OCD cases obsessions and compulsions often serve mixed functions. Can the inclusion of cognitive variables provide further insights into the function of obsessive and compulsive symptoms thereby offering a stronger conceptual framework for defining OCD subtypes? At this point it is unclear whether there will be substantial progress in developing a solid OCD subtype classification based on cognitive-behavioral considerations. The OC-relevant beliefs and appraisals identified by the Obsessive Compulsive Cognitions Working Group (1997), for example, are highly intercorrelated and most are not specific to OCD. Our measures of these constructs are still in an initial stage of development. On the other hand, if a more contextualized and functional analysis of obsessive and compulsive symptoms is needed in order to develop a truly valid OCD subtype classification, then the assessment of faulty appraisals and beliefs could play an integral role in this enterprise.
A Cognitive Approach to OCD Subtypes If distinct diagnostic subtypes exist within OCD, then we might expect certain symptoms or cognitive phenomena to manifest categorical rather than di-
COMMENTARY:
LUMPING
mensional characteristics. Haslam et al. (2005) present the first taxometric analysis of OCD cognition and symptom variables. Employing a large OCD sample, they investigated whether contamination, checking, and obsessionality symptom-based subtypes might occur in responses to the Padua Inventory (PI) and whether responsibility/threat estimation, perfectionism/intolerance of uncertainty, and importance/control of thoughts cognition-based subtypes could be derived from the Obsessive Beliefs Questionnaire (OBQ). Evidence for the categorical nature of these variables was not overwhelming. Contamination, responsibility/threat, and perfectionism/intolerance of uncertainty exhibited strong and consistent dimensionality. Results for checking and pure obsessionality were less consistent, with some weak indication that discrete latent subclasses exist. The strongest evidence for a taxonic model was found for importance/control of thoughts, yet even here the findings were not entirely consistent. Overall, though, support for dimensionality was much stronger than for the existence of categorical symptom or cognition variables in OCD. The findings from this study have direct implications on the subtype issue in OCD. If OCD cognition and symptom variables are primarily dimensional in nature, then it will be much harder to form meaningful discrete subtypes of the disorder. The alternative might be the development of some form of profile analysis where individuals with OCD vary along primary symptom and cognition dimensions. At this stage it would be premature to abandon categorical research of OCD simply on the basis of the somewhat discouraging findings from initial taxometric analysis.
Treatment of OCD Subtypes The final article in this series by Sookman et al. (2005) discusses treatment implications of adopting a subtype classification of OCD. The authors state that standard exposure and response prevention (ERP) outcome studies regard OCD as a homogeneous group, which obscures whether different symptom subtypes vary in their treatment response. Their review of ERP outcome studies suggests that certain subtypes, such as obsessional rumination without overt compulsion and individuals with hoarding compulsions, may not respond as well to treatment. Sookman et al. suggest that a shift toward a more cognitive orientation in treatment might improve efficacy, especially for patients with checking or hoarding compulsions, or those with obsessions and no overt compulsions. Two cognitive-behavior therapy (CBT) studies are presented in which specific beliefs and appraisals for different OCD subtypes were targeted for change.
VS.
SPLITTING
403
Sookman et al. conclude that CBT for OCD could be improved by developing manualized treatment for OCD subtypes that target faulty beliefs and appraisals that characterize each subtype. Although the call for more research on the treatment of OCD subtypes is important, I am not sure the "pay-off" in terms of enhanced interventions will be as significant as expected. First, the ERP and CBT interventions developed for OCD more generally have proven quite adaptable and robust to more specific manifestations of the disorder. For example, Abramowitz et al. (2003) found that ERP was equally effective in treating the harming obsession, contamination, unacceptable thoughts and symmetry subtypes (based on a cluster analysis of the YBOCS checklist) but not the hoarding cluster. In addition, some of the studies reviewed by Sookman et al. (2005) indicate that ERP-based treatment can be effective for subtypes like obsessional ruminators. Based on the empirical data, it is not clear that the development of specialized CBT for OCD subtypes would improve treatment outcome, with the possible exception of hoarding. Second, Sookman et al. (2005) advocate an idiographic approach to the treatment of OCD subtypes. But is this not what we already do when we develop a case formulation as part of CBT for OCD (see Clark, 2004)? Subsequent cognitive and ERP strategies are then tailored to the unique symptom presentation and cognitive profile of the patient. I am not sure that manualized treatments for specific OCD subtypes will lead to better interventions unless CBT practitioners have abandoned case conceptualization and failed to tailor their interventions to the unique characteristics of individual clients. Finally, the high correlations among OC belief domains cast further doubt on whether specialized treatment approaches for specific cognitive or symptom presentations is a viable option. Instead of viewing inflated responsibility, overestimated threat, importance and control of thoughts, or perfectionism and intolerance of uncertainty as distinct appraisal and belief domains, it is more precise to view them as overlapping constructs that capture a slightly different perspective on how individuals endow unwanted intrusive thoughts and obsessions with meaning and personal significance. Conclusion The search for reliable subtypes of OCD addresses a fundamental question about the nature of this disorder. The articles in this special series raise the possibility that a greater focus on the faulty appraisals and beliefs that have been identified as pathognomonic in OCD might yield more precise and reliable OCD subtypes. In this commentary I
404
CLARK
have suggested a number of reasons why the inclusion of cognitive variables may not address the problems evident when subtyping is based entirely on symptom content. Naturally, it would be premature to abandon subtype research in OCD because our work on this issue is still in its infancy. On the other hand, it would also be naYve to assume that research and treatment of OCD subtypes will automatically advance our understanding and response to OCD. Some form of profiling based on symptom and cognition dimensions may be the better alternative for OCD research and treatment. In the meantime we must await further research to judge the merits of subtyping in OCD. References Abramowitz, J. S., Franklin, M. E., Schwartz, S. A., & Furr, J. M. (2003). Symptom presentation and outcome of cognitivebehavioral therapy for obsessive-compulsive disorder. Journal of Consulting and Clinical Psychology, 71, 1049 - 1057. Brown, T. A. (1998). The relationship between obsessivecompulsive disorder and other anxiety-based disorders. In R. P. Swinson, M. M. Antony, S. Rachman, & M. A. Richter (Eds.), Obsessive-compulsive disorder: Theory, research and treatment (pp. 207-226). New York: Guilford Press. Calamari, J. E., Wiegartz, P. S., & Janeck, A. S. (1999). Obsessive-compulsive disorder subgroups: A symptom-based clustering approach. Behaviour Research and Therapy, 37, 113-125. Calamari, J. E., Wiegartz, P. S., Riemann, B. C., Cohen, R. J., Greer, A., Jacobi, D. M., Jahn, S. C., & Carmin, C. (2004). Obsessive-compulsive disorder subtypes: An attempted replication and extension of a symptom-based taxonomy. Behaviour Research and Therapy, 42, 647-670. Clark, D. A. (2004). Cognitive-behavioral therapy for OCD. New York: Guilford Press. Freeston, M. H., Ladouceur, R., Gagnon, E, Thibodeau, N., Rheame, J., Letarte, H., & Bujold, A. (1997). Cognitivebehavioral treatment of obsessive thoughts: A controlled study. Journal of Consulting and Clinical Psychology, 65, 405-413. Frost, R. O., & Steketee, G. (1998). Hoarding: Clinical aspects and treatment strategies. In M. A. Jenike, L. Baer, & W. E. Minichiello (Eds.), Obsessive-compulsive disorder: Practical management (3rd ed., pp. 533-554). St. Louis: Mosby Press. Haslam, N., Williams, B. J., Kyrios, M., McKay, D., & Taylor,
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ACCEPTED: February 1, 2005