Obsessive– Compulsive Disorder 463
Hypothesis 1
The unwanted intrusive thoughts, images, or impulses related to the obsessional concerns
of individuals with OCD will be more frequent and intense or salient than the unwanted
intrusive thoughts with similar obsessive content that occur in individuals without OCD..
Numerous studies have administered either self- report questionnaires or interview
checklists and found that the vast majority of nonclinical individuals experience, at
least occasionally, unwanted intrusive thoughts, images, or impulses that are similar in
content to clinical obsessions (e.g., Freeston, Ladouceur, Thibodeau, & Gagnon, 1991;
Parkinson & Rachman, 1981a; Purdon & Clark, 1993; Rachman & de Silva, 1978;
for reviews, see Clark & Rhyno, 2005; Julien et al., 2007). This finding has been rep-
licated in countries other than those located in North America such as Korea (Lee &
Kwon, 2003), Spain (Belloch, Morillo, Lucero, Cabedo, & Carrió, 2004b), Italy (Clark,
Radomsky, Sica, & Simos, 2005), and Turkey (Altin, Clark, & Karanci, 2007).
There is some preliminary evidence that questionnaires may actually underestimate
the frequency of obsession- relevant intrusive thoughts in nonclinical samples when more
open-ended interviews are employed (D. A. Clark et al., 2005). Although the continu-
ity between nonclinical and clinical intrusive thought content was recently challenged
in a content analysis conducted by Rassin and Muris (2006), there is still consider-
able empirical support for the universality of obsession- relevant intrusive thoughts. As
expected, studies that compare individuals with OCD and nonclinical samples have
found that nonclinical individuals have significantly less frequent, distressing, unac-
ceptable, and uncontrollable intrusions than their clinical counterparts (e.g., Calamari
& Janeck, 1997; Rachman & de Silva, 1978; Morillo et al., 2007). As predicted, the
frequency, distress, and uncontrollability of intrusions correlates more highly with mea-
sures of OCD symptoms but moderate correlations have also been found with general
anxiety, worry, and depression (see reviews by D. A. Clark & Rhyno, 2005; Julien et al.,
2007). A recent information- processing experiment involving reaction time in a word
recognition task revealed that individuals with OCD showed stronger facilitation (i.e.
encoding) and weaker inhibition when processing threat and neutral stimuli (Bannon,
Gonsalvez, & Croft, 2008). The authors argued that the combination of strong encoding
and weak inhibition might perpetuate obsessionality by making vulnerable individuals
more responsive to obsessive-like intrusive thoughts and compulsive behaviors. Overall,
then, empirical support for Hypothesis 1 is strong. Even though nonclinical individuals
have mental intrusions with similar content to obsessions, those with OCD have more
frequent and intense unwanted intrusive thoughts, images, and impulses and they may
be cognitively primed to process these internal stimuli more intensely.
Hypothesis 2
Individuals with OCD will have significantly higher endorsement of maladaptive beliefs in
personal responsibility, overimportance of thoughts, overestimated threat, need to control
thoughts, intolerance of uncertainty, and perfectionism than individuals without OCD.
A number of self- report OCD belief measures have been developed such as (1) the
Responsibility Attitudes Scale (RAS) to assess general beliefs about responsibility and the