The Vancouver Obsessional Compulsive Inventory (VOCI)

Abstract

The original Maudsley Obsessional Compulsive Inventory (MOCI) has been widely used and is considered to be one of the best available self-report instruments for measuring observable obsessive–compulsive problems such as washing and checking. However, it has several limitations and requires updating. Our revision of the MOCI, the Vancouver Obsessional Compulsive Inventory (VOCI), was designed to provide assessment of a range of obsessions, compulsions, avoidance behaviour, and personality characteristics of known or theoretical importance in obsessive–compulsive disorder (OCD). The development of the VOCI is described, and we provide evidence of its reliability and validity. Our findings in samples of people with OCD, people with other anxiety disorders or depression, community adults, and undergraduate students suggest that the VOCI is a promising new measure. We anticipate that, like its predecessor, the VOCI will have widespread use in both research and clinical settings.

Introduction

The MOCI (Hodgson & Rachman, 1977) is a widely used self-report instrument for measuring observable compulsive behaviour such as washing and checking. It contains 30 true/false items, with subscales for cleaning, checking, doubting/conscientiousness, and obsessional slowness. Over the past 25 years, the MOCI has demonstrated adequate internal consistency, with good criterion, convergent, and discriminant validity (e.g., Emmelkamp, Kraaijkamp and van den Hout, 1999, Richter, Cox and Direnfeld, 1994). Despite its longevity as a clinical research instrument with sound psychometric properties, the MOCI has several limitations, and requires modernizing as it was constructed in the “pre-cognitive era.” First, the slowness subscale has been criticized as being neither internally consistent nor factorially distinct (Emmelkamp, 1988, Taylor, 1998). Second, assessment of obsessive–compulsive phenomena other than washing and checking is limited (e.g., obsessions, hoarding, covert rituals). Third, although originally designed as a research instrument, it has often been used to assess therapeutic change; however, the MOCI is not well suited to measuring changes with treatment, both because of its dichotomous response format, and because several items refer to past and permanent events rather than current behaviour and concerns (e.g., My parents were rather strict). Finally, in order to control for the confounding effects of response set, which was a major but exaggerated concern in 1977, half the items in the MOCI were negatively worded; since a number of items are worded as double negatives, patients often complain that they are difficult to understand, and scoring can be confusing.

Other self-report measures of OCD-related thoughts and behaviour also have drawbacks. The original Padua Inventory (Sanavio, 1988) contained four subscales: checking, contamination fears, mental dyscontrol, and fear of behavioural dyscontrol. Several items were found to be measuring worry rather than obsessions, and the scale was revised by Burns, Keortge, Formea and Sternberger (1996). Their revised scale, the Padua Inventory-Washington State University Revision, comprised five subscales: obsessional thoughts about harm to oneself or others, obsessional impulses to harm oneself or others, contamination obsessions and washing compulsions, checking compulsions, and dressing and grooming compulsions. The revised Padua Inventory has good psychometric properties and is one of the most comprehensive self-report measures of OCD, but several important groups of symptoms are not covered, such as hoarding. The Obsessive–Compulsive Inventory (OCI; Foa, Kozak, Salkovskis, Coles, & Amir, 1998) is a newer inventory that assesses the frequency and distress associated with washing, checking, doubting, ordering, obsessing, hoarding, and mental neutralizing. However, both patients and clinicians have expressed some difficulty with the rating requirements of the OCI, as each item is rated on two dimensions (frequency and distress). Some patients report that this double-rating is somewhat confusing and repeatedly ask for information about how to complete the scale, while others simply take a very long time to complete it. Given that patients with OCD are often extremely slow at completing questionnaires (Rachman & Hodgson, 1980), it would be preferable to administer a questionnaire without a double-rating requirement.

Our revision of the MOCI, the Vancouver Obsessional Compulsive Inventory (VOCI) was designed to provide assessment of a wider range of obsessions, compulsions, avoidance behaviour, and personality characteristics of known or theoretical importance in OCD, and to refine it in the light of developments over the past two decades. Each item is rated on a five-point Likert-type scale to enhance its sensitivity to therapeutic change. All items refer to current concerns and behaviour, and are positively cued, leading to easier administration, scoring, and interpretation. The development of the new scale began in 1994, and followed a construct-based approach through several stages of development, including both factor- and item-analytic strategies. Importantly, the scale is expanded beyond its original behaviourist basis and now includes cognitive items.