Symptom Stability in OCD
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Background: Attempts to address the heterogeneity of OCD has yielded 3-5 OCD dimensions via factor analytic studies. Per the authors, prior studies have suggested a relationship between certain dimensions and socio demographic, genetic, and physiologic variables. If patients remain stable within a dimension, thereby decreasing the heterogeneity of OCD, further information about the neurobiology of OCD can be obtained. However, prior studies have shown that OCD symptoms change over time. This study attempts to answer 1) Are individual symptoms of adult OCD stable across time? 2) Are previously identified symptom dimensions of OCD stable? 3) Are some symptoms more stable than others? 4) Can changes be attributed to the effects of treatment? 5) Do changes occur within symptom dimensions, or, are there shifts from one dimension to another?
Methods:
Design - Naturalistic Prospective Study.
Setting - Three specialized university-based (Brown, Yale, and Harvard [MGH]) OCD clinics
Patient Population - Inclusion criteria were age of 18 years or older and a willingness to be followed for 2 years. The diagnosis of OCD was confirmed in all cases by experienced interviewers through use of a structured diagnostic interview. ( Patients with comorbid diagnoses were not excluded if OCD was the dominant disorder) The study yielded a sample of 117 patients.
Description of OCD symptoms-The 10-item clinician-rated Yale-Brown Obsessive Compulsive Scale and the Yale-Brown Obsessive Compulsive Scale symptom checklist which consist of 50 items which are separated into 13 OCD categories. The patients' scores on the five symptom dimensions were computed by summing the scores of the symptom categories under each dimension; these scores were then used in all subsequent data analyses. The five symptom dimensions were symmetry/ordering, hoarding, contamination/ cleaning, aggressive/checking, and sexual/religious obsessions. Analysis -
- For each individual Yale-Brown Obsessive Compulsive Scale symptom category, McNemar's tests were used to determine the significance of changes in symptoms.
- To analyze changes in symptom severity (10-item Yale-Brown Obsessive Compulsive Scale) and within the five previously identified OCD symptom dimensions, comparisons of the current symptoms at baseline and at 6-month, 1-year, and 2-year follow-ups were made. Then they were applied to repeated measures analyses of variance.
- The percent decrease from baseline to 2-year follow-up on the total Yale-Brown Obsessive Compulsive Scale score was included as a covariate in the analyses to address changes within symptom dimensions confounded by overall reduction in OCD severity attributable to treatment.
- A series of stepwise multiple regression models were tested in which each symptom dimension at a given follow-up point was the dependent variable and all five OCD symptom dimensions at the immediately preceding follow-up point were entered as independent variables to assess the degree of change between previously identified OCD symptom dimensions, (Significance level was set at p<0.01 to control for possible type I errors due to multiple testing. )
Follow-up -Of the initial group of patients, 81(69%) attended their respective clinics at 6-month follow up, 83 (71%) at 1-year follow-up, and 67 (57%) at 2-year follow-up. There were no statistically significant differences in baseline characteristics between subjects who did or did not participate in the follow-up evaluations. Accounting for dropouts was not addressed.
Validity:
Definition of patient sample-The study didn't address whether the same experienced clinical interviewer interviewed at each site. The study did not address the structured clinical interview used. Variations in demographics were not given only the number of men and women, mean age and scores. There was no information about time since onset of OCD symptoms for the patients.
Is the study representative of clinical practice-NO. The study was performed at specialized OCD clinics at university hospitals
Was duration of follow-up sufficient? Information about treatment was available only from 2 sites where
66 patients had SRI's for 12 weeks or more and 12 patients had had an "adequate" trial of behavior therapy. Were all patients accounted for? NO
Were outcome criteria objective and unbiased relative to the OCD symptoms? NO. The training of the clinician or blinding to treatment was not addressed in the study.
Was their adjustment for linked OCD symptoms? YES. OCD symptoms determined which dimension the patient was placed.
Were patients in the study treated similarly? Unlikely considering some patient's received behavioral therapy and others had medication management.
Results
- McNemar's tests showed that the symptoms of some patients changed significantly from baseline to 6month follow-up. When using p<0.01 Changes were more likely to occur in aggressive obsessions, as well as in cleaning, checking, counting, ordering, and hoarding compulsions. When we used a less stringent 0.05 significance level, changes were observed in contamination, hoarding, and symmetry obsessions as well. Only cleaning showed a significant change outside of the first six months. (Table 1)
- Repeated measures ANOVAs showed significant differences over time on the aggressive/checking (F=9.94, df=3, 150, p 1]0.001), symmetry/ordering (F=6.43, d=3, 150, p= 0.001), and contamination/cleaning (F=4.16, df-3,150, p=0.007) dimensions. The hoarding and sexual/religious dimensions remained mostly unchanged across time (Fig 1). Repeated measures ANOVAs found significant improvements on the Yale-Brown Obsessive Compulsive Scale total score from pretreatment (mean=20.7, SD--9.6) to 2-year follow-up (mean=15.8, SD=8.9) (F= 10.66, epsilon-corrected df=1.9, 85.1, p00.001).
- Repeated measures analyses with the percent drop on the total Yale-Brown Obsessive Compulsive Scale over the 2-year period as a_covariate yielded non significant covariance coefficients, suggesting that changes within symptom dimensions of OCD were independent from the overall reduction in symptom severity.
- Multiple regression analyses showed strong partial correlations between each OCD symptom dimension at a given follow-up point and the same dimension at the immediately previous point, whereas significant correlations between different dimensions were rare and small (Table 2) There were strong partial correlation between each OCD symptom dimension at different follow-up points with respect to baseline scores on the same dimension. Overall, most partial correlation were greater than 0.60 the only exception was the aggressive/checking dimension, which had the smallest partial correlations across time.
Strengths and Weaknesses of Study- The study did not differentiate the patient's on the basis of the type of treatment they received. Moreover, the frequency and duration of patient contact during this treatment was not addressed. Of note, the information about the patients' treatment was not available given that the MGH did not have the information available. The was question of reliability of diagnosis in using SCII) and whether the clinicians administering the 10 item scale were blinded to the patient's follow up schedule or the type of treatment the patient was receiving. There was no explanation of how the information from the clinicians 10-item scale was incorporated into the study. There was question about accounting for patients in the studied, which appear to have fluctuated at follow-ups. Demographic similarity of the patient's was not addressed in the study. Analysis of information from drop out was not addressed. There was no indication that the patient's were treated similarly not only between sites but within sites also.
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