Obsessive-Compulsive Inventory

The Obsessive-Compulsive Inventory (OCI)

Devised By: Foa, Kozak, Salkovskis, Coles, and Amir (1998).

Type of Instrument: A new self-report inventory for determining the diagnosis and overall severity of obsessive-compulsive disorder (OCD), and yields a profile of frequency and distress for each symptom class. Intended to be applicable to the general population in assessing subclinical obsessional thoughts and behaviours.

Administration: Administration requires no technical expertise and typically takes 15 minutes.

Rationale for development: The OCI was developed:

To be more comprehensive than other available instruments by encompassing 7 subscales that address the heterogeneity of obsessions and compulsions observed in OCD.

To allow for a wide range of severity scores to afford comparisons among the severity of various obsessions and compulsions

To provide an instrument that can be more readily administered to both clinical and non-clinical populations.

Note: the following psychometric data is published by the authors in the one article, which reports 3 studies. Study 1 (Content Validity and Internal Consistency) and Study 3 (Discriminative and Convergent Validity) use the same four samples, that is participants: 114 individuals with OCD, and individuals, with other anxiety disorders, that is 44 with posttraumatic stress disorder (PTSD), 58 with generalised social phobia (GSP), and 194 nonpatient controls.

Study 2 (Test-Retest Reliability) results are based on analysis of data collected from the following participants: 41 with OCD (8 of whom participated in Study 1) and 57 nonpatient controls, all of whom participated in Study 1. The intertest interval was approximately 2 weeks for people with OCD and 1 week for controls.

Reliability

Split-half / Cronbach's Alpha: Internal consistency – Full scales and most subscales have satisfactory internal consistency. The alpha coefficients of the full scale for each group were all high (range .86 to .95), indicating the distress and frequency items within each subscale converge on a common construct.

Regarding the subscales - All but 6 of the 56 coefficients exceeded .70.
Intercorrelation among symptom subscales and total score for the OCD sample were generally lower than those in the other samples. This is explained as possibly due to the heterogeneity of the symptom presentation among individuals with OCD, such that they typically exhibit high scores on some subscales and low scores on others. People with OCD were expected to exhibit low scores on all of the OCI subscales.
Overall high internal consistency was demonstrated for the subscales except for the Neutralizing subscale, which had modest internal consistency in the non-OCD samples. The authors suggest this may reflect restricted range rather than structural inadequacy because neutralizing is rare in individuals without OCD.
Of interest, distress and frequency were more positively correlated in the OCD group than in the non-OCD groups, suggesting that although individuals without OCD sometimes experience intrusive ideas and perform superstitious actions, they do not report being so distressed by them as do those with OCD. These results are consistent with findings reported by Rachman and DeSilva (1978).

Test-Retest Reliability: Overall reliability for total scores and subscale scores were satisfactory, with good test-retest reliability for total scores of symptoms frequency and distress in individuals with OCD and in non-patient populations.

High test-retest reliability for the distress (OCD, r=.87; controls, r=.89) and frequency (OCD, r=.84; controls r=.90) total scores.

Test-retest reliability for the subscales exceeded .80, with the exception of the Ordering distress (r=.77), and Ordering frequency scores (r=.79) in the OCD sample and the Doubting distress (r=.77), and Hoarding distress (r=.68) scores in the control sample.

Alternate Form Reliability: NA

Inter-rater Reliability: Interrater reliability was not assessed directly in this study. Previous research that used this same assessment method at the same Center has revealed satisfactory interrater agreement for the Y-BOCS severity score (Foa et al., 1995).

Validity:

Criterion (or Predictive) Validity: NA

Content Validity: Foa, Kozak and Salkovskis formulated the original item pool. Seven subscales were constructed to represent the major symptoms of OCD as found in DSM-IV (APA, 1994) field trial for OCD (Foa et al., 1995).

Convergent Validity: The Y-BOC, MOCI, and CAC were used to assess the convergence of the OCI with existing measures of OCD.

The OCI correlates well with other measures of OCD symptoms and distinguishes individuals with OCD from those with other anxiety disorders and controls. Positive correlations of the OCI total score with the total scores of the MOCI and the CAC. These findings suggest that athough the OCI assesses a wider range of OCD symptoms than other OCD questionnaires, this does not compromise reliability in assessing OCD severity. The Washing and Checking subscales of the MOCI are also positively correlated.

Discriminant Validity: Measures used to assess the divergence of the OCI from measures of depression (BDI and HAM-D), severity of anxiety (BAI), and state and trait anxiety (STAI).
- Comparison of groups on distress:

A 4(Group: OCD, GSP, PTSD, NPC) x 7 (Subscales: Washing, Checking, Doubting, Odering, Obsessing, Hoarding, Mental Neutralizing) multivariate analysis of variance (MANOVA) revealed main effects of Group, F(,317)=55.96, p<.001, and subscale, F(6,312)=28.53, p<.001), Pillai’s = 0.35; that were modified by a Group x Subscale interactions, F(18,942) = 4.58, p<.001, Pillai’s = 0.24. The OCD group reported more distress than other groups on all but the Hoarding subscale, on which the OCD group scored higher than the PTSD and GSP groups but not the controls.

Comparison of groups on frequency:

The OCD group reported more frequent OCD symptoms than did the remaining 3 groups on all but Hoardings subscale.

A 4(Group) x 7 (Subscale) MANOVA revealed significant main effects of group, F(3,256) = 22.29, p<.001, and subscale, F(6,260) = 17.08, p<.001, Pillai’s = .28; modified by an interaction of Group x Subscale; F(18,786) = 5.83, p<.001, Pillai’s = 3.5.

Comparison of groups on frequency and distress:

As expected, PTSD, GSP, and control groups scored higher on frequency ratings, while the OCD group scored high on both types of ratings. A 4 (Group) x 2 (Rating: frequency, distress) ANOVA on the OCI total revealed significant effects of group, F(3, 184) = 24.21, p<.001, and rating, F(1,184) = 94.96, p<.001, modified by a Group x Rating interaction, F(3,184) = 6.38, p<.001.

Simple effects analyses are reported also for each of the above.

Overall discriminant validity:

The OCI demonstrates good discriminant validity: total OCI distress and frequency for the OCD group exceeded those in the GSP, PTSD and control groups. Subscale scores were also higher for the OCD group except for Hoarding. The Hoarding items do not adequately distinguish pathological hoarding from ordinary collecting, and this subscale requires revision.
Moderate correlations of the OCI with measures of depression and general anxiety as compared with high correlations of the OCI with the MOCI and CAC support its divergent validity. Although there is some shared variability, the OCI measures more than depression and anxiety.

Scoring Method:

Each item is rated 0-4 on a Likert scale provides a wide range of severity for each item and each subscale. Scores include total distress and frequency and subscale frequency and distress.
There are 7 subscales

Norms:

People who presented to The Center for the Treatment and Study of Anxiety, Philadelphia, Pennsylvania for evaluation of OCD completed a series of self-report questionnaires including the OCI. Diagnosis of OCD was completed in two stages. First stage comprised a 2 hour interview with a doctoral level clinical psychologist experienced in diagnosing OCD. The assessment interview included the Y-BOCS (Goodman et al., 1989) and the Hamilton Depression Scale (HAM-D; Hamilton, 1960). On completion, the interview data was presented to a senior clinician and a Stage two assessment confirmatory interview was completed with a senior clinician (Edna B. Foa, Michal J. Kozak). Average age of participants with OCD was 33.2 years, 51 percent were women.

Other samples included individuals, with other anxiety disorders, that is posttraumatic stress disorder (PTSD), average age was 30.9 year, 100 percent were women; generalised social phobia (GSP), average age was 38.7 years, 45 percent were women; and nonpatient controls, average age was 20.3 years, 67 percent were women.

All individuals evaluated for PTSD and GSP at the Center also completed a series of self-report questionnaires including the OCI, followed by a structrued clinical interview (SCID; First et al., 1995).

Nonpatient volunteers were recruited from university undergraduate, graduate and medical students and hospital staff. Students scored in the normal range on the Beck Depression Inventory (BDI; Beck, Steer, & Garbin, 1988) and the Spielberger State-Trait Anxiety Inventory (STAI; Speilberger, 1983). Hospital staff received the SCID and had no Axis 1 diagnoses.

Participants in Study 2 with OCD had a mean age of 34.3 years; 31percent were women. Controls had a mean age of 19.3 years; 93% were women.

The full normative data are available here.

Measures for Diagnoses:

The SCID III-R (Spitzer, Williams, Gibbon & First, 1990) and SCID-IV (First, Spitzer, Gibbon & Williams, 1995) are semistructured diagnostic interviews to determine DSM-III-R (APA, 1987) and DSM-IV (APA, 1994) diagnoses. Both interviews are administered by a clinician and include introduction and distinct modules. Results record the presence or absence of each disorder being considered for both a current episode and lifetime history.

The Y-BOC (Goodman et al., 1989) ia a semi-structured interview that assesses severity and treatment responses of OCs. The scale has excellent psychometric properties for core items (DeVeagh-Geiss, Landau & Katz, 1989; Goodman et al., 1989) but it is limited by the requirement of administration by a trained interviewer, and does not provide information about the specific content of the obsessions and compulsions (Foa et al., 1998).

Measures regarding Study 3 Discriminative and Convergent Validity:

In addition to the OCI, and before the diagnostic interview, participants completed the MOCI, the CAC the BDI, the Beck Anxiety Inventory (BAI; Beck, Epstein, & Steer, 1988), and the STAI. These scales are described below:

The Maudsley Obsessive-Compulsive Inventory (MOCI) (Hodgson & Rachman, 1977) is a 30 item true-false self-report questionnaire that assesses overt rituals and their related obsessions and includes four subsclaes. The scale has satisfactory test-retest reliability (r = .80) and internal consistency (.70 and .80; Rachman & Hodgson, 1980). Four subscales were identified through factor analysis: Washing, Checking, Slowness and Doubting. Scores for each item indicate severity of each symptom class. Satisfactory external validity was found for Washing and Checking subscales, but support for the Slowness and Doubting subscales was weaker. Two limitations of the MOCI are (a) the true-false format restricts the sensitivity of the scale to severity of specific symptoms and thus to change on posttreatment, and (b) the items of the MOCI encompass only two of the behavioural complusions (i.e. checking and washing) and sdo not tap specific obsessions other than contamination. Thus, Foa et al., (1998) conclude that although the MOCI seems to address the heterogeneity of OCD through its four subscales than do other available instruments, the subscales capture only a subset of OCD symptoms, and only two (i.e. washing and checking) are of demonstrated validity.

The Compulsive Activity Checklist (CAC) (Freund et al., 1987) consists of 38 items. This scale focusses on specific behaviours that assess compulsions.

The Beck Depression Inventory (BDI; Beck, Steer, et al., 1988) is a 21-item self-report scale used to assess cognitive and physical symptoms of depression.

The Beck Anxiety Inventory (BAI; Beck, Epstein, et al., 1988) is a 21 item self-report inventory designed to assess the severity of anxiety symptoms in adults and adolescents. Two factors identified are Somatic and Subjective Anxiety or Panic, which have good internal consistency, test-retest reliability, and convergent and divergent validity.

The Spielberger State-Trait Anxiety Inventory (STAI); Spielberger, 1983) is a 40-item self-report scale, with 20 items assessing state anxiety and 20 items assessing trait anxiety.

Cautions:

The Hoarding subscale requires revision to differentiate excessive hoarding from routine collecting, and thus increase its discriminative validity.

As a result of evaluations conducted in the current study (Foa et al., 1998), plans were made to evaluate the sensitivity of the OCI to treatment effects.

Plans were also made to develop a shorter version of the OCI to make it more useful as a screen for OCD in a variety of settings.

The scale has only been evaluated in one study, Foa et al., 1998.

Samples varied between psychometric property evaluations; that is the sample utilised for test-retest reliability data differed from the sample which provided data for the other property evaluations.

Appendix A

Seven subscales were constructed to represent the major symptoms of OCD as found in the Diagnostic and Statistical Manual of Mental Disorders (4^th ed.:DSM-IV; American Psychiatric Association, 1994) field trial for OCD (Foa et al., 1995).

Each item is rated on 0-4 Likert scale for frequency of occurrence and distress.

The subscales are:

Washing – 8 items; e.g., "I think contact with bodily secretions (perspiration, saliva, blood, urine, etc.) may contaminate my clothes or somehow harm me".

Checking – 9 items; e.g., "I repeatedly check doors, windows, drawers, etc".

Doubting – 3 items; e.g., "I ask people to repeat things to me several times, even though I understood them the first time".

Ordering – 5 items; e.g., "I need things to be arranged in a particular order".

Obsessing – 8 items; e.g., "I have thoughts that I may want to harm myself or others".

Hoarding – 3 items; e.g., "I collect things I don’t need".

Mental neutralizing – 6 items; e.g., "I need to pray to cancel thoughts or feelings".

References

American Psychiatric Association. (1987). Diagnostic and statistical manual of mental disorders (3^rd ed., rev.). Washington, DC: Author.

American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4^th ed.). Washington, DC: Author.

Beck, A.T., Epstein, N., Brown, G., & Steer, R.A. (1988). An inventory for measuring clinical anxiety: Psychometric properties. Journal of Consulting and Clinical Psychology, 56, 893-897.

Beck, A.T., Steer, R.A., & Garbin, M.G. (1988). Psychometric properties of the Beck Depression Inventory: Twenty-five years of evaluation. Clinical Psychology Review, 8, 77-100.

Foa, E.B., Kozack, M.J., Goodman, W.K., Hollander, E., Jenke, M.A., & Rasmussen, S. (1995). DSM-IV field trial: Obsessive-compulsive disorder. American Journal of Psychiatry, 152, 90-96.

Foa, E.B., Kozak, M.J., Salkovskis, P.M., Coles, M.E., and Amir, N. (1998). The validation of a new obsessive-compulsive disorder scale: The Obsessive-Compulsive Inventory. Psychological Assessment, 10(3), 206-214.

First, M.B., Spitzer, R.L., Gibbon, M., & Williams, J.B.W. (1995). Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-IP). Washington, DC: American Psychiatric Press.

Freund, B., Stekee, G.S., & Foa, E.B. (1987). Compulsive Activity Checklist (CAC): Psychometric analysis with obsessive-compulsive disorder. Behavioural Assessment, 9, 67-79.

Goodman, W.K., Price, L.H., Rasmussen, S.A., Mazure, C., Fleischmann, R.L., Hill, C.L., Heninger, G.R., & Charney, D.S. (10=989). He Yale-Brown Obsessive Compulsive Scale: I. Development, use, and eliability. Archives of General Psychiatry, 46, 1006-1011.

Hodgson R,J,, & Rachman, S. (1977). Obsessional-compulsive complaints. Behavioural Research and Therapy, 15, 389-395.

Rachman, S., & Hodgson, R.J. (1980). Obsessions and compulsions. Englewood Cliffs, NJ: Prentice Hall.

Rachman, S., & DeSilva, P. (1978). Abnormal and normal obsessions. Behaviour Research and Therapy, 16, 23-248.

Speilberger, C.D. (1983). Manual for the State-Trait Anxiety Inventory (Form Y). Palo Alto, CA: Consulting Psychologists Press.

Spitzer, R.L., Williams, J.B., Gibbon, M., & First, M.B. (1990) Structured Clinical Interviews for DSM-III-R – Patient Edition. Washington, DC: American Psychiatric Press.

Above written by: Ms. Trish Earle

Reviewed, edited and approved by: Dr. Grant J. Devilly