Symptom dimensions and cognitivebehavioural. therapy outcome for pediatric obsessive-compulsive

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1 Acta Psychiatr Scand 2008: 117: All rights reserved DOI: /j x Copyright Ó 2007 The Authors Journal Compilation Ó 2007 Blackwell Munksgaard ACTA PSYCHIATRICA SCANDINAVICA Symptom dimensions and cognitivebehavioural therapy outcome for pediatric obsessive-compulsive disorder Storch EA, Merlo LJ, Larson MJ, Bloss CS, Geffken GR, Jacob ML, Murphy TK, Goodman WK. Symptom dimensions and cognitivebehavioural therapy outcome for pediatric obsessive-compulsive disorder Objective: To examine whether obsessive-compulsive disorder (OCD) symptom subtypes are associated with response rates to cognitivebehavioural therapy (CBT) among pediatric patients. Method: Ninety-two children and adolescents with OCD (range = 7 19 years) received 14 sessions of weekly or intensive (daily psychotherapy sessions) family-based CBT. Assessments were conducted at baseline and post-treatment. Primary outcomes included scores on the ChildrenÕs Yale-Brown Obsessive-Compulsive Scale (CY- BOCS), remission status, and ratings on the Clinical Global Improvement (CGI) and Clinical Global Impression Severity (CGI- Severity) scales. Results: Seventy-six per cent of study participants (n =70)were classified as treatment responders. Patients with aggressive checking symptoms at baseline showed a trend (P = 0.06) toward improved treatment response and exhibited greater pre post-treatment CGI- Severity change than those who endorsed only nonaggressive checking symptoms. Step-wise linear regression analysis indicated higher scores on the aggressive checking dimension were predictive of treatment-related change in the CGI-Severity index. Regression analysis with CY-BOCS score as the dependent variable showed no difference between OCD subtypes. Conclusion: Response to CBT in pediatric OCD patients does not differ substantially across subtypes. E. A. Storch 1,2, L. J. Merlo 1, M. J. Larson 3, C. S. Bloss 4, G. R. Geffken 1,2, M. L. Jacob 1, T. K. Murphy 1, W. K. Goodman 1 Departments of 1 Psychiatry, 2 Pediatrics and 3 Clinical and Health Psychology, University of Florida, Gainesville, FL and 4 University of California, San Diego and San Diego State University Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA Key words: obsessive-compulsive disorder; symptom dimensions; cognitive-behavioural therapy; children; treatment; factor analysis Eric A Storch, Department of Psychiatry, University of Florida, Gainesville, FL 32610, USA. estorch@psychiatry.ufl.edu Accepted for publication September 25, 2007 Significant outcomes Response to CBT in pediatric OCD patients does not differ substantially across subtypes. There is some evidence that patients with checking rituals and harm obsessions have a better response to CBT. Limitations Analyses for some subgroups (i.e., hoarders) may have been underpowered. There was significant overlap among symptom categories, with most patients displaying multiple symptoms. Although this may result in more ecologically valid analyses (i.e., most patients presenting for treatment have multiple symptoms), it prevented us from examining between-group differences because groups were not independent. Obsessive-compulsive disorder (OCD) in children and adolescents is a relatively prevalent disorder (1, 2) that is accompanied by significant disability (3). In as many as 80% of cases, symptoms appear in childhood or adolescence (4). Without treatment, pediatric OCD typically runs a chronic 67

2 Storch et al. course into adulthood (5, 6). Fortunately, important advances have been made in the pharmacological and psychological interventions for OCD, improving patient treatment and prognosis (7). Considering the heterogeneous presentation of adult and pediatric OCD and how this might impact treatment, attention has been paid to symptom subtypes that might have more or less favorable treatment outcomes. Primarily, subtypes have been identified through factor analytic studies of the Yale-Brown Obsessive-Compulsive Scale (Y- BOCS; 8, 9) Symptom Checklist. Such studies have produced fairly consistent results, with four- or five-factor solutions comprising dimensions of: i) symmetry ordering, ii) contamination cleaning, iii) sexual religious obsessions, iv) aggressive checking, and v) hoarding dimensions (10). It remains unclear if the sexual religious obsessions and aggressive checking dimensions are a single factor or two separate factors. The limited data for children also support this general factor structure (11). Prospective studies over 2 (12) and 6 years (13) have supported the stability of these OCD symptom dimensions. To examine differential cognitive-behavioural therapy (CBT) response as a function of patient subtype, several past studies in samples of adult patients have used categorical approaches in which patients are divided into mutually exclusive groups. Patients with hoarding symptoms have shown worse response to CBT (14) and combined CBT and pharmacotherapy (15). The presence of primarily obsessional symptoms has also been linked to less favorable CBT outcome (5). Relative to other symptom domains, generally favorable outcomes have been found for washing and checking compulsions (14, 16, 17). In contrast to the categorical approach, a dimensional approach, which allows patients to potentially be included on multiple dimensions, has unique advantages including improved generalizability (e.g., most patients have multiple symptoms in multiple categories) and feasibility. Yet, only a few studies of this sort have been reported for adult patients. For example, among 104 adults treated with in-patient CBT, Rufer et al. (18) found worse response in patients with hoarding symptoms and patients with sexual religious obsessions. Similar results were found in a post-hoc analysis of 153 adults treated with either computer- or clinicianadministered CBT (17). Finally, in 354 out-patient adults treated with a serotonin reuptake inhibitor, hoarding symptoms were associated with less favorable treatment response (19). To our knowledge, there are no published studies that have explored the relationship between dimensional subgroups of OCD and CBT treatment outcome in pediatric patients. Such work would contribute to the growing literature focused on predicting response to CBT for pediatric OCD by elucidating subtypes with a more favorable or less favorable prognosis. Aims of the study In the present study, we examined the extent to which symptom dimensions were associated with CBT response in a sample of youth with OCD. Based on results of studies examining adult OCD patients, we predicted that higher scores on the hoarding and the sexual religious obsessions dimension would predict less favorable CBT response. Material and methods Participants Participants included 92 children and adolescents ages 7 19 years old (mean = 13.6 ± 3.3) who consecutively presented for CBT at the University of Florida OCD Program over the period of Fifty-three per cent were male (n = 49), and the majority of participants were Caucasian in ethnicity (n = 87), followed by Asian (n = 3) and Hispanic (n = 2). Inclusion criteria were: i) principal diagnosis of OCD and ChildrenÕs Yale Brown Obsessive-Compulsive Scale (CY-BOCS; 20) Total Score 16; ii) no change in psychotropic medication (if applicable) for at least 8 weeks prior to study entry; and, iii) availability of at least one parent to accompany the child to all sessions. Exclusion criteria were: i) history of and or current psychosis, bipolar disorder, or current suicidality; ii) principal diagnosis other than OCD; iii) diagnosis of autism or mental retardation based on records review and clinical interview; iv) in concurrent psychotherapy of any kind; and v) caregiver diagnosis of mental retardation, psychosis, or other psychiatric disorders or conditions that would limit their ability to participate in their childõs treatment. Fifty-nine per cent of youth had a comorbid psychiatric condition, with the specific comorbidities as follows generalized anxiety disorder (n = 33), major depression (n = 24), attention deficit hyperactivity disorder (n = 23), oppositional defiant disorder (n = 14), social phobia (n = 14), TouretteÕs syndrome (n = 9), panic disorder (n = 5), and trichotillomania (n = 1). Forty-three per cent of youth had more than one comorbidity. Sixty-four per cent of subjects (n = 59) were on psychotropic medication for 68

3 Symptom dimensions their OCD at the baseline assessment. Medications consisted of varied selective serotonin reuptake inhibitors, with a minority of children also on atypical antipsychotics (n = 17). Medication remained stable throughout the course of treatment and participants were not allowed to receive concurrent psychotherapy. Measures Anxiety Disorder Interview Schedule for Children Parent Version. The ADIS-IV-P (21) is a semi-structured diagnostic interview that assesses DSM-IV anxiety, mood, and externalizing disorders in youth. Diagnoses are based on symptom endorsement and a severity rating of 4 on an 8- point scale. Studies investigating the psychometric properties have shown positive results (22, 23). ChildrenÕs Yale Brown Obsessive Compulsive Scale. - Based on the adult Yale-Brown Obsessive-Compulsive Scale (8, 9), the CY-BOCS (20) is a 10-item, clinician-rated semi-structured interview that assesses OCD symptom severity over the past week. The CY-BOCS includes the following four sections Obsessions Checklist, Severity Items for Obsessions, Compulsions Checklist, and Severity Items for Compulsions. From these sections, an Obsession Severity score (five items), Compulsion Severity score (five items), and Total Score (sum of all 10 items) are yielded. On the Obsessions and Compulsions Symptom Checklists, 54 obsessions and compulsions are rated for their current and past presence (scored as 1) or absence (scored as 0). Considered the Ôgold standardõ for pediatric OCD assessment, the CY-BOCS has strong supporting reliability and validity data (20, 24, 25) and documented treatment sensitivity (26 28). Clinical Global Improvement. The Clinical Global Improvement scale (CGI; 29) reflects the evaluatorõs assessment of treatment progress relative to the baseline assessment. The CGI is rated on a 7- point scale ranging from 1 (very much improved) to 7 (very much worse). For the current study, treatment response was defined as receiving a rating of Ôvery much improvedõ or Ômuch improved.õ Clinical Global Impression-Severity. The Clinical Global Impression Severity scale (CGI-S; 30) is a clinician rating of symptom severity. Ratings range from 1 (Ôno illnessõ) to 7(Ôextremely severeõ). The CGI-S correlates strongly with the CY-BOCS Total Score (r = 0.75) in pediatric OCD patients (24), and is widely used and treatment sensitive (27, 28). Procedures The procedures for this study were approved by the University of Florida Institutional Review Board. All participants had a principal diagnosis of OCD, according to DSM-IV-TR (31) criteria, made by the first or second author. Diagnoses were made using best-estimate procedures (32), which included an unstructured clinical interview by the first or second author, results from the ADIS-IV-P and CY-BOCS. Ninety-nine per cent (92 93) of families agreed to participate in study-related procedures. Baseline demographic and clinical characteristics of the sample are included in Table 1. Assessments. After obtaining appropriate written consent and assent, trained masters or doctoral level clinical psychology doctoral students administered clinician-rated measures (ADIS-IV-P, CY- BOCS, CGI-S) to parents and children jointly. Clinician ratings were based on parent and child responses, as well as clinician judgment and behavioural observation of the child. The first author trained all raters in measurement administration as follows: i) direct instruction, ii) observation of at least three training cases, iii) administration of three batteries under direct supervision. To evaluate inter-rater reliability, the CY-BOCS was readministered to 20 children and their parents at baseline; inter-rater reliability was high for the total score (kappa = 0.96). Following Table 1. Baseline demographic and clinical characteristics in 92 children and adolescents with OCD Variables Mean (SD) Age in years 13.6 (3.3) Number of OCD patients, n (%) Gender, female male ( ) Frequencies of obsessions on the CY-BOCS Symptom Checklist (%) Contamination 48 (52.2) Aggressive 30 (32.6) Somatic 29 (31.5) Religious 20 (21.7) Sexual 19 (20.7) Hoarding 11 (12.0) Magical thoughts superstitions 9 (9.8) Frequencies of compulsions on the CY-BOCS Symptom Checklist (%) Rituals involving other persons 35 (38.0) Washing cleaning 33 (35.9) Checking 31 (33.7) Order arranging 25 (27.2) Repeating 24 (26.1) Counting 21 (22.8) Hoarding 13 (14.1) Magical superstitious behavior 5 (5.4) 69

4 Storch et al. administration of clinician-rated measures, parents and children completed secondary measures that are not reported in this study. Immediately following treatment, these assessment procedures were replicated for each patient. The literature on symptom dimensions has produced generally consistent results, with studies among adults showing four- or five-factor solutions. Generally, the symptom dimensions of contamination washing, symmetry ordering, and hoarding were consistent across studies. However, some studies found that the aggressive checking and sexual religious dimensions form a single factor (33, 34) whereas others have found support for separate factors (10, 35, 36). Given that the evidence reviewed in Mataix-Cols et al. (10) supports the validity of a five-factor model of symmetry ordering, contamination cleaning, sexual religious obsessions, aggressive checking, and hoarding, and that Mataix-Cols et al. (17) and Rufer et al. (18) used these dimensions in their analyses (thus, enhancing comparability of results), we chose to use the five-factor dimensional model of OCD. Consistent with Mataix-Cols et al. (17) and Rufer et al. (18), the current presence of a primary symptom on the CY-BOCS Symptom Checklist was coded as 1; its absence was coded as 0. Scores on the five-factor analytically derived symptom dimensions (symmetry ordering, contamination cleaning, sexual religious obsessions, aggressive checking, and hoarding) were derived by summing the scores of the symptom categories for each dimension. Cognitive-behavioural therapy. Participants received weekly (n = 48) or intensive (n = 42) familybased CBT. For 40 youth, the treatment format was based on their participation in a study involving a randomized comparison of weekly and intensive CBT (28); for the others, this was based on clinical appropriateness. At baseline, weekly and intensive treatment patients differed on mean age (intensive: 12.4 years; weekly 14.7 years; t(90) = 2.55, P < 0.02) and CGI-S score (intensive CGI = 5.2; weekly CGI = 4.8; t(90) = 3.46, P < 0.01). Groups did not differ on gender ratio or number of participants with comorbid conditions (both v 2 < 1.15, P > 0.28) nor did they differ on CY-BOCS Total Score, CY- BOCS Obsessions Scale, CY-BOCS Compulsion Scale, mean household income, or any symptom dimensions (all t-values <1.73, all P-values >0.09). In addition, medication was equally distributed across groups (v 2 = 1.46, P=0.23), and no outcome differences as measured by the CGI-S, CGI-I, and CY-BOCS were found across intensive or weekly conditions (t-values <1.42, P-values >0.16). Thus, in order to achieve adequate statistical power for the analyses of interested, intensive and weekly treatment groups were combined. Therapy included 14 individual 90-min CBT sessions in either a weekly (once per week) or intensive (14 sessions over 3 weeks) format. Therapists were clinical child psychology postdoctoral fellows and or doctoral candidates who were under the first authorõs supervision. All therapists had treated at least three OCD cases prior to serving as a therapist. Training included guided reading of the treatment protocol, and completing at least three training cases with integrity checks independently under supervision. Supervision was held between sessions and as needed otherwise. Sessions were conducted according to a modified version of the Pediatric Obsessive-Compulsive Disorder Treatment Study (POTS; 27) manual and included psychoeducation, cognitive training, and exposure with response prevention (E RP). Slightly different from the original POTS protocol, sessions were delivered in a Ôfamily-basedÕ format, with at least one parent attending all sessions with the patient. Consistent with work by Freeman et al. (37), parents were included in the treatment to facilitate understanding of treatment principles, to assist with generalization of treatment gains by enlisting the parent as an at-home Ôcoach,Õ to reduce parent accommodation of OCD symptoms, and to encourage optimal effort by the child during in-session exposures and homework assignments. During the first three sessions, the cognitivebehavioural model of OCD was discussed. An exposure and response prevention hierarchy was also created, which ranked ritual-producing stimuli from least to most distressing on the Subjective Units of Distress Scale. In session 4, the child selected a trial exposure of relative ease. Thereafter, CBT sessions consisted of gradual exposure (both imaginal and in vivo) to hierarchy items, with instructions for strict abstinence from compulsions. Early exposures were to moderately distressing situations with progression toward more anxiety-provoking ones. During exposures, therapists directed attention to youthsõ mistaken cognitions about the likelihood of catastrophic consequences. Between-session homework was assigned ( 60 min daily) consisting of exposures to stimuli similar to those addressed in session. Parts of the final two sessions were used to prepare the patient to manage symptoms independently. Potential barriers and problem situations were also reviewed, accompanied by a discussion of the appropriate action. Treatment plans were 70

5 Symptom dimensions individually tailored to address patient-specific symptoms, as well as other needs (e.g., family accommodation, oppositionality, parent child communication problems, developmental needs). For younger children, fewer and less sophisticated cognitive components were included in the treatment. Additionally, younger children often required more parental involvement (e.g., reduced accommodation) and contingency management strategies (e.g., rewards for participation in E RP exercises). Data analysis As only 7 out of 92 participants dropped out of treatment and the primary reason for drop-out was lack of improvement, we used last observation forward analyses to account for missing data at the post-treatment assessment. A within-subjects, repeated-measures analysis of variance was employed to examine changes in CY-BOCS Total Score, CY-BOCS Obsession Severity, and CY- BOCS Compulsion Severity from baseline to posttreatment. Response to CBT was defined as a rating of 1 (very much improved) or 2 (much improved) on the CGI at post-treatment. PearsonÕs chi-squared and independent samples t-tests were used for between-group (treatment responders vs. treatment non-responders) comparisons. For both categorical and dimensional OCD subtype analyses, endorsement of any symptoms within a particular dimension was sufficient for inclusion in that subgroup; thus, patients were included in multiple subgroups. For dimensional analysis of OCD symptom subgroups, we utilized the approach of Rufer et al. (18), where variables representing symptom severity for each of the five symptom dimensions of the CY-BOCS were computed separately for each dimension (i.e., hoarding: range 0 2 symptoms, symmetry arranging: range 0 5 symptoms, contamination: range 0 13 symptoms, sexual religious: range 0 5 symptoms, and aggression checking: range 0 12 symptoms). The use of dimensional subgroups and subsequent inclusion of single participants in multiple groups renders omnibus between-group tests inappropriate because of violations of the assumption of group independence. Thus, separate PearsonÕs chisquared analyses within each symptom endorsement group (e.g., patients who endorsed hoarding symptoms compared with patients who did not endorse hoarding symptoms) were performed on treatment response data. In addition, separate independent samples t-tests were used for comparisons of CY-BOCS and CGI-Severity pre posttreatment difference scores. We then conducted a stepwise binary logistic regression analysis using forward technique to examine dimensional predictors of treatment response or non-response. Two subsequent step-wise linear regression analyses using forward technique were conducted to examine OCD symptom dimensions as potential predictors of pre post-treatment changes in CGI- Severity and CY-BOCS Total Scores. For each stepwise regression, factors with an F-value lower than 3.84 (P =0.05) were eliminated. Due to the exploratory nature of this study, all significance values were set at P < 0.05 (two-sided). Results Baseline demographic and clinical characteristics of study participants are listed in Table 1. The most frequent symptoms observed in this sample were contamination and aggressive obsessions, rituals involving other persons, and washing cleaning and checking compulsions. Participants generally displayed a significant decrease from baseline to post-treatment on CGI-Severity [4.9 ± 0.9 to 2.9 ± 1.3; F(1,91) = 191.3, P < 0.001], CY- BOCS Total Score [27.4 ± 5.9 to 11.8 ± 90.0; F(1, 91) = 278.2, P < 0.001], CY-BOCS Obsession Severity score [13.6 ± 3.3 to 6.3 ± 4.5; F(1, 91) = 237.8, P < 0.001], and CY-BOCS Compulsion Severity score [13.8 ± 3.2 to 5.5 ± 4.9; F(1, 91) = 277.0, P < 0.001]. Seventy-six per cent of study participants (n =70) were classified as treatment responders based upon a CGI-Improvement rating of 1 or 2. Demographic information, chi-squared or t-values, and significance level for analyses as a function of treatment response group are presented in Table 2. Treatment responders and non-responders did not differ on the demographic variables of sex, age, or family income, nor did they differ in the number of patients with comorbid diagnoses, baseline CGI- Severity or CY-BOCS Total, Obsession Severity, or Compulsions Severity scores. As expected, treatment responders showed significant decreases in CGI-Severity and all CY-BOCS scores relative to non-responders. Results of pre post-treatment outcome measures as a function of OCD symptom group are presented in Table 3. In order to examine group response to treatment, separate chi-squared analyses were conducted using treatment response status as the dependent variable and categorical OCD symptom group (e.g., patients with aggressive checking symptoms vs. patients without aggressive checking symptoms) as the independent variable. Results indicated that patients with aggressive checking symptoms at baseline showed 71

6 Storch et al. Table 2. Demographic and pre post-treatment clinical characteristics as a function of treatment response group. Data include mean (SD) unless otherwise specified Demographic Variable Response (n =70) Non-response (n =22) t or v 2 P-value Sex (male), n (%) 37 (53) 12 (55) Age 13.6 (3.5) 13.7 (2.9) ) Family income (44 993) (36 898) ) Comorbid condition present, n (%) 39 (56) 15 (68) Baseline CGI-Severity 5.0 (.9) 4.9 (.9) Baseline CY-BOCS Total Score 27.5 (5.8) 27.3 (6.7) Baseline CY-BOCS Obsession Severity 13.6 (3.1) 13.5 (4.2) Baseline CY-BOCS Compulsion Severity 13.8 (3.1) 13.8 (3.5) Post-CGI-Severity 2.4 (.8) 4.7 (1.1) ) Post-CY-BOCS Total 7.9 (5.1) 24.0 (7.9) ) Post-CY-BOCS Obsession Severity 4.5 (2.7) 12.0 (4.2) ) Post-CY-BOCS Compulsion Severity 3.5 (2.8) 12.0 (4.6) ) Pre post-difference CGI-Severity 2.6 (1.1) 0.2 (0.6) Pre post-difference CY-BOCS Total 19.6 (5.9) 3.2 (4.9) Table 3. Clinical improvement for OCD patients within each symptom endorsement group. Data include mean (SD) unless otherwise specified CGI-Severity CY-BOCS Total Score Symptom endorsement group Baseline Post Baseline Post Response rate (%) Hoarding (n =14) 5.1 (1.0) 3.0 (1.7) 29.6 (5.8) 14.9 (11.7) 64.3 Symmetry order (n = 44) 5.1 (0.9) 2.9 (1.5) 28.5 (5.5) 12.4 (10.3) 75.0 Contamination (n = 48) 4.9 (1.0) 2.9 (1.2) 27.6 (6.2) 12.0 (8.6) 77.1 Sexual religion (n = 51) 5.1 (1.0) 3.0 (1.3) 28.0 (5.8) 12.0 (9.0) 72.5 Aggression checking (n = 61) 5.1 (0.9) 2.8 (1.3) 27.5 (6.2) 11.1 (8.8) 82 a trend toward being more likely to respond to treatment than those who endorsed only nonaggressive checking symptoms (v 2 (1) = 3.4, P=0.06). No differences in the per cent of treatment responders were found for those who differentially endorsed hoarding, symmetry order, contamination, or sexual religious symptoms and those who did not (all chi-squared values < 1.3, all P-values >0.26). Similarly, separate independent samples t-tests were conducted using the pre posttreatment difference score for CGI-Severity or CY- BOCS Total Score as the dependent variable, and symptom group as the independent variable. Results of the t-tests for each categorical symptom endorsement group indicated patients who endorsed aggressive checking symptoms had greater pre post-treatment CGI-Severity change than those who did not endorse such symptoms (t(90) = 2.0, P < 0.05); the same difference was not reliable for CY-BOCS difference score (t(90) = 1.2, P=0.22). No differences on pre post-change scores for either the CGI-Severity index or CY-BOCS Total Score were found for the other four symptom endorsement groups (all t-values <0.97, all P-values >0.34]. To examine the symptom dimensions continuously, rather than as categorical variables, participantsõ dimensional scores for each OCD subtype (e.g., symmetry ordering, contamination cleaning, sexual religious obsessions, aggressive checking, and hoarding) were first entered into a stepwise binary logistic regression with treatment response (defined as a post-treatment CGI-S score of Ôvery muchõ or ÔmuchÕ improved) as the dependent variable and OCD symptom dimensional scores as the independent variables. Two subsequent separate step-wise linear regressions with the dependent variables of pre post-treatment difference score on the CGI-Severity index and pre post-treatment differences score on the CY- BOCS, respectively, as the dependent variables were also conducted. For the stepwise logistic regression, no significant predictors were retained in the model based on our established criteria. Subsequent linear regression analyses indicated that higher scores on the aggressive checking dimension were predictive of treatment-related change in the CGI-Severity index (b = 0.34, P < 0.05, 95% CI = ). No significant predictors were retained in the model for the second regression predicting pre post-treatment change in CY-BOCS Total Score. Discussion The present study examined cognitive behavioural therapy outcome among children and adolescents with varying symptom subtypes of OCD 72

7 Symptom dimensions (i.e., symmetry ordering, contamination cleaning, sexual religious obsessions, aggressive checking, and hoarding symptoms). In general, CBT was effective for youth with all symptom subtypes. In fact, the overwhelming majority (76%) were rated as Ômuch improvedõ or Ôvery much improvedõ after 14 CBT sessions, supporting the assertion that CBT should be recommended as the first-line treatment for youth with OCD (e.g., 27), regardless of presenting symptoms. However, the consistently observed positive treatment response among the current sample created a Ôceiling effect,õ making between-group comparisons of treatment outcome difficult to detect. For example, although similar studies in adults indicated less favorable treatment outcome among patients with hoarding symptoms or sexual religious symptoms (17, 18), these differences were not statistically significant in the present study. It is noteworthy that youth with hoarding symptoms displayed the lowest treatment response rates (i.e., 64.3%), followed by youth with sexual religious symptoms (i.e., 72.5%). Unfortunately, given the relatively small number of study participants (e.g., only 14 youth displayed hoarding symptoms), the analyses were not adequately powered to support our hypotheses. The present results suggest that some of the same factors affecting adult OCD patients with these symptoms (e.g., poor insight) may affect pediatric OCD patients as well. Patients with hoarding symptoms or primarily religious symptoms may have more difficulty recognizing the irrational nature of their symptoms than other patients, likely due to the longer delay between the anxietyprovoking stimulus and the feared consequences. For example, while patients with contamination symptoms may be concerned about becoming sick immediately following contact with a contaminated object, patients with hoarding symptoms may worry about throwing an item away in case they need it weeks, months, or years later. Similarly, patients with religious obsessions are typically more concerned about long-term consequences (e.g., suffering post-mortem for eternity) than short-term consequences. As a result, these beliefs are more difficult to challenge and or disprove, because the feared consequence could still occur long after the exposures have been completed. On the other hand, the group of children presenting with aggressive checking symptoms stood out as significantly more likely that the others to respond to treatment, with 82% displaying positive treatment response. Applying the same logic, the length of time between the onset of the obsession and the feared consequence is typically quite short. Anxiety levels typically fall quickly when the individual refrains from engaging in a checking compulsion and no negative consequence occurs. Similarly, individuals who are afraid of acting out an aggressive impulse typically learn quickly upon exposure to the feared stimulus that they are able to maintain control. Building upon operant conditioning theory (38), these symptoms may be more amenable to extinction with exposure and response-prevention, because of the close temporal connection between behavior (e.g., exposure) and punishment (e.g., feared consequence). Participation in the exposure, followed immediately by negative reinforcement (e.g., gradually decreasing anxiety), results in increased willingness to engage in future exposures. Some limitations of the study should be noted. First, in order to achieve adequate statistical power we combined OCD patients who were treated with either intensive or weekly CBT. However, groups did not differ on post-treatment response variables or any symptom dimensions, but they did differ on initial CGI-S score. It is possible, however, that results are biased by the type of treatment received, which may be one explanation for the inconsistency of these data with past adult studies (17, 18). Second, the sample was composed of a relatively homogeneous group of individuals; namely, primarily Caucasian youth from upper middle-class backgrounds who presented to a specialty treatment clinic for OCD. As a result, the results may not generalize to the population of youth with OCD as a whole. Third, as noted previously, the limited number of participants presenting with certain symptom subtypes (e.g., hoarding) likely resulted in the analyses for that group being underpowered. Fourth, in an effort to broadly cover possible treatment outcomes, the CGI, CGI- S, and CY-BOCS all were utilized as outcome measures. Finding differences in treatment response as a function of symptom dimension in the CGI-S, but not CY-BOCS, shows some inconsistency in OCD severity measurement. However, it is common in clinical trials to utilize both the CGI scales and CY-BOCS as outcome measures (e.g., 39, 40). Furthermore, studies have found a strong, but not perfect, relationship between the CGI-S and CY-BOCS (24) suggesting that these scales assess overlapping but somewhat different constructs. Factor analytic studies of the CY- BOCS and Y-BOCS have identified separate dimensions of illness severity and symptom resistance control (41 43) with data suggesting that the severity dimension is more strongly related to the CGI-S rating than resistance control (42). Thus, 73

8 Storch et al. while the CGI-S and the CY-BOCS tend to be highly correlated there are differences in the constructs that they measure. Finally, there was significant overlap among symptom categories, with most patients displaying multiple symptoms. Although this may result in more ecologically valid analyses (i.e., most patients presenting for treatment have multiple symptoms), it prevented us from examining between-group differences because groups were not independent. Declaration of interest The authors have no competing interests with this study. Acknowledgement The contributions of Emily Ricketts and Valerie Crawford are acknowledged. References 1. Maina G, Albert U, Bogetto F, Ravizza L. Obsessive-compulsive syndromes in older adolescents. Acta Psychiatr Scand 1999;100: Zohar AH. The epidemiology of obsessive-compulsive disorder in children and adolescents. Child Adolesc Psychiatr Clin N Am 1999;8: Piacentini JC, Bergman RL, Keller M, McCracken J. 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