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J. Behav. Ther. & Exp. Psychiat. 43 (2012) 855e861
Contents lists available at SciVerse ScienceDirect
Journal of Behavior Therapy and
Experimental Psychiatry
journal homepage: www.elsevier.com/locate/jbtep
Dissolving the tenacity of obsessional doubt: Implications for treatment outcome
Frederick Aardema a, b, *, Kieron O’Connor a
a
b
University of Montreal, Fernand-Seguin Research Center, 7331 Hochelaga, Montreal, Québec H1N 3V2, Canada
Concordia University, Montreal, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 August 2011
Received in revised form
1 December 2011
Accepted 12 December 2011
Background and objectives: Previous research has found that a high impact of possibility based information during reasoning prevents the resolution of doubt among those with Obsessive-Compulsive
Disorder (OCD). It was expected that the ability of those with OCD to resolve obsessional doubt would
improve following Inference Based Treatment (IBT).
Methods: The ability to resolve doubt, including the relative impact of reality and possibility based
information, was measured before and after treatment with the Inference Processes Task in a group of 35
participants diagnosed with OCD.
Results: Results confirmed that IBT improved the participants’ ability to resolve obsessional doubt. Those
who improved their ability to resolve doubt showed a significantly better treatment outcome.
Improvements appeared mostly due to a lowered impact of possibility based information following
treatment.
Limitations: The study did not include a control condition although results clearly indicate that the ability
to resolve obsessional is closely linked to the most relevant quantifiers of treatment outcome. In addition,
relatively small sample sizes prevented more powerful multiple comparisons between groups.
Conclusions: Results suggest treatment implications and the relevance of dissolving the tenacity of
obsessional doubt in OCD.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Obsessive-compulsive disorder
Doubt
Possibility
Imagination
Inference based therapy
Treatment outcome
1. Introduction
Obsessive-compulsive disorder (OCD) is a disorder characterized by frequent obsessions and compulsions with a debilitating
effect on overall functioning and well-being. Current cognitive
approaches propose that obsessions find their origin in unwanted
intrusive thoughts, which if appraised negatively, lead the person
to try to “neutralize” with compulsive behaviours (Rachman, 1997;
Salkovskis, 1985).
However, it has also been suggested that intrusive thoughts, or
obsessions, often take the form of a doubt, focussing on a possible
state of affairs in reality (e.g. “I might have left the stove on”, “I
might be contaminated”, “I might be dangerous”) (O’Connor, 2002).
These doubts often occur out of any related context and do not
necessarily require any subsequent appraisal in order to increase
anxiety and motivate compulsive behaviours (Grenier, O’Connor, &
Bélanger, 2008; Julien, O’Connor, & Aardema, 2009).
* Corresponding author. University of Montreal, Fernand-Seguin Research Center,
7331 Hochelaga, Montréal, Québec H1N 3V2, Canada. Tel.: þ1 514 251 4015; fax: þ1
514 251 2617.
E-mail address: [email protected] (F. Aardema).
0005-7916/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jbtep.2011.12.006
In the last decade, experimental research on OCD has supported
the role of doubt in OCD, mostly with regards to self-defeating
maintaining behaviours that increase memory distrust and lower
confidence (Ashbaugh & Radomsky, 2007; Dar, Rish, Hermesh, Fux, &
Taub, 2000; van den Hout & Kindt, 2003, 2004). A more general lack
of cognitive confidence or conviction has been implicated as well,
including a distrust of perception and attention, making doubts and
compulsive behaviours more likely (Hermans et al., 2008; Lazarov,
Dar, Oded, & Liberman, 2010). Other studies have suggested that it
may not be a general lack of confidence, but instead that underconfidence is restricted to specific OCD related domains (Moritz,
Rietschel, Jelinek, & Bäuml, 2011; Moritz et al., 2007).
One cognitive theory, termed an inference based approach (IBA),
has offered an account of obsessions that considers doubt not only
to be a discrete OCD-related process, but also the principal characteristic of OCD (O’Connor, Aardema, & Pélissier, 2005). In this
model, obsessions are considered virtually synonymous with
doubts that take the form of an inference about a possible state of
affairs in reality that is preceded by a subjective narrative characterized by a distrust of the senses and an overreliance on the
imagination. These two inferential components consisting of dismissing reality and favouring hypothetical possibilities together
constitute an “inferential confusion” where the person with OCD
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gives credibility to a specific doubt despite lack of evidence in
reality.
Take the following narrative of a patient with OCD (From
O’Connor & Aardema, 2011):
“I have to check my stove each time I leave my apartment
because I know I am an absent-minded person and that I can
forget things. It even happened once that I forgot a pot on my
stove; it could have set fire to my apartment. Also, I heard that
a fireman forgot a pot on a stove right at the fire station and it set
fire to the station. It is reasonable to think that if a fireman
forgets pots on stoves, it could happen to anybody and especially
to those like me who tend to be absent-minded.”
The hallmark of such obsessional narratives is the weight
accorded to ‘maybes’ - that is, to hypothetical possibilities. The
narratives convincingly replace confidence in the senses (and the
self) with a doubting inference based on remote possibilities, which
lead the person astray from a common sense approach. Moving the
person away from these subjective narratives, including the reliance on remote possibility, are important targets for an Inference
Based Therapy (IBT; see O’Connor & Aardema, 2011; O’Connor,
Koszegi, Aardema, Van Niekerk, & Taillon, 2009).
A recent treatment trial has shown IBT to be a viable alternative
to more established treatments like cognitive appraisal therapy or
exposure in vivo with response prevention (O’Connor, Aardema,
Bouthillier et al., 2005). Indeed, empirical research on mechanisms of change during IBT has shown that improvements during
therapy coincide with changes in inferential confusion as measured
by the Inferential Confusion Questionnaire (Aardema, Emmelkamp,
& O’Connor, 2005; Aardema, O’Connor, Emmelkamp, Marchand, &
Todorov, 2005; Aardema, Wu, Careau, O’Connor, & Dennie, 2010).
Also, experimental research utilizing the Inference Processes Task
(IPT) has shown that levels of doubt are a direct function of the
impact of possibility based information during reasoning which in
turn relates to levels of inferential confusion (Aardema, O’Connor,
Pélissier, & Lavoie, 2009).
During the IPT participants are alternately presented with
possibility and reality based information in relation to an obsessional doubt as induced by a hypothetical scenario. Those with OCD
are similarly affected by reality based information as compared to
non-clinical controls, but significantly more influenced by possibility based information, leading to higher levels of doubt (Aardema
et al., 2009). Moreover, in the IPT, those with OCD typically do not
reach any resolution and arrive at higher end-point levels of doubt
than non-clinical controls, showing a higher impact of possibility
during their reasoning leading the person to perseverate and
persist in obsessional doubts even though they are completely
unrelated to reality.
Improving the client’s ability to find resolution to obsessional
doubt is one of the main goals of IBT. Yet, little is known on whether
a person’s ability to resolve doubt by targeting the inferential
confusion process is affected by cognitive therapy, or whether
indeed it is even relevant to treatment outcome. IBT leads to clinical
improvement, and psychometric studies support the mechanism of
change to be inferential confusion. Yet, so far, this process has not
yet been measured in an experimental task such as the IPT before
and after treatment.
Differentiating between a relatively heterogeneous group of
people with OCD in terms of their varying abilities in resolving
doubt would constitute a powerful test of the link between doubt
resolution and inferential confusion. In other words, rather than
looking at changes in a heterogeneous group, a stronger test
controlling for random variation might be to compare clinical
outcome in groups defined according to resolution ability. Indeed,
previous research with the IPT has shown that a proportion of
people with OCD is able to resolve doubt even before treatment has
commenced (Aardema et al., 2009). The majority, however, appears
less able, and shows higher end point levels of doubt as compared
to non-clinical controls.
The current study attempts to answer the question as to
whether improvement in the ability to resolve obsessional doubt
during reasoning as measured by the IPT is linked to treatment
outcome. Specifically, it is expected that 1) Following IBT the
person’s ability to resolve obsessional doubt will improve; 2)
Change in the ability to resolve doubt is associated with treatment
outcome; and 3) Improvements in the person’s ability to resolve
doubt is associated with a lessened impact of possibility based
information during reasoning.
2. Method
2.1. Recruitment and participants
Thirty-five participants (age 18e65) meeting DSM-IV-TR diagnostic criteria for OCD (APA, 2000) participated in the present study
as part of a treatment outcome study on IBT conducted at the OCD
Spectrum Study Centre located at the Fernand Seguin Research
Center in Montreal, Canada. All participants that completed the IPT,
the main experimental task of the present study, before and after
treatment, were included in the study. Before administration of the
IPT, participants were recruited and assessed by a two-stage
process using telephone screening interviews followed by initial
questionnaires returned by mail and a face-to-face diagnostic
interview. The face-to-face diagnostic interview used three structured interviews to provide adequate description of clinical
features by a trained evaluator independent of the study. First, all
participants were administered the Structured clinical interview for
DSM-IV-TR (SCID-I) (First et al., 2002) - a structured interview that
diagnoses axis I disorders that provides excellent coverage of the
more common exclusionary conditions such as primary mood
disorders, substance and alcohol dependence and abuse, somatoform disorders, and screens for psychotic features. Second, participants were administered the Yale-Brown Obsessive-Compulsive
Scale (Y-BOCS; Goodman, Price, Rasmussen, Mazure, Delgado et al.,
1989; Goodman, Price, Rasmussen, Mazure, Fleischmann et al.,
1989). Third, personality disorders were assessed with the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCIDII) (First, Gibbon, Spitzer, Williams, & Benjamin, 1997). Entry criteria
were: (a) a primary diagnosis, according to DSM-IV-TR criteria, of
OCD (b) no other principal axes 1 disorders, (c) no change in
medication type or dose during the 12 weeks before treatment for
antidepressants (4 weeks for anxiolytics), (d) willingness to keep
medication stable while participating in the study, (e) no evidence
of suicidal intent, (f) no evidence of current substance abuse, (g) no
evidence of current or past schizophrenia, bipolar disorder or
organic mental disorder (h) no other concomitant psychological
treatment while participating in the study. The final sample consisted of 16 males and 19 females. The average age was 41.3 years
(SD ¼ 11.57; range 23e65). Educational levels were distributed as
follows: 14.3% high school, 22.9% College (i.e. Cégep in Québec),
11.4% Bachelor’s degree, 17.1% Master’s degree or higher.
2.2. Inference based treatment
Following diagnosis, all eligible participants were offered a 24week course of IBT in accordance with published guidelines
(O’Connor & Aardema, 2011; O’Connor et al., 2009). Unlike most
other cognitive behavioural therapies, IBT is entirely cognitive in
nature, and does not include exposure and response prevention.
The first four sessions were evaluation sessions of the client by the
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F. Aardema, K. O’Connor / J. Behav. Ther. & Exp. Psychiat. 43 (2012) 855e861
therapist in order to tailor IBT to the specific needs of the client. The
remaining 20 sessions consisted of IBT formulated and delivered in
a 10-step format utilizing worksheets and exercise sheets.
During treatment, all participants were seen by one of three
therapists assigned to the client. Sessions lasted for the duration of
1 h on a weekly basis. Clients received therapy from the same
therapist throughout treatment. All therapists were licenced clinical psychologists with previous training and experience in IBT. In
addition, therapists received weekly supervision from the principal
investigators.
Participants were evaluated by an independent trained assessor
after 14 sessions, to evaluate whether there were any contraindications to continuing treatment (worsening of condition, new
condition, motivation problem, inability to progress in current
treatment). If there were contra-indications, the participant was
withdrawn from the research program and referred to more
appropriate standard management. At the end of treatment, after
24 sessions, clients were referred to other resources for further
treatment and follow-up if necessary.
2.3. Measures
The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS; Goodman,
Price, Rasmussen, Mazure, Delgado et al., 1989; Goodman, Price,
Rasmussen, Mazure, Fleischmann et al., 1989). The Y-BOCS is the
instrument of choice for clinician assessment of OC symptoms and
severity and served as principal treatment outcome measure. The
Y-BOCS consists of three parts: a symptom checklist, a description
of target symptoms for each individual, and a structured rating of
obsessions and compulsions plus insight and reliability ratings.
Studies confirm the validity and reliability of the principal scales
(Steketee, 1994; Taylor, 1995). For the current study, the Y-BOCS was
administered by an independent assessor at pre-, mid-, posttreatment. The time delay between then initial Y-BOCS evaluation
and the start of sessions with the therapist was on average three
weeks. Post-treatment assessment also occurred on average within
one week following the last session.
The Padua Inventory (PI; Sanavio, 1988) is a self-report measure
that consists of 60 items that measures both classic compulsive
checking and cleaning behaviour as well as various types of obsessions. Items are rated on a 5-point scale (0 ¼ not at all to 4 ¼ very
much). Studies with the PI have reported good reliability for the total
scale as well as convergent and discriminant validity with high
correlations with other measures of OCD and moderate correlations
with anxiety and depression (Sanavio, 1988; Sternberger & Burns,
1990). The PI, like any of the other measures, was administered
before and after treatment. Pre-treatment, they were completed by
the clients during the four session evaluation phase before IBT
treatment commenced. Post-treatment, they were completed within
two weeks after the last session with the therapist.
The Beck Depression Inventory-II (BDI-II) The BDI-II (Beck, Steer &
Brown, 1996) is a 21-item measure designed to assess the severity
of depressive symptoms experienced by respondents during the
two weeks previous to completion. It is a frequently used and
highly reliable and valid measure of symptoms of Depression (Beck
et al., 1996).
The Beck Anxiety Inventory (BAI; Beck, Epstein, Brown, & Steer,
1988) is a 21-item (0e3 scale) anxiety intensity symptom
measure experienced in the last week. The instrument shows high
internal consistency (a ¼ 0.91), good test-retest reliability
(r ¼ 0.75), moderate convergent validity with the revised Hamilton
Anxiety Rating Scale (r ¼ 0.51) and discriminant validity with the
Hamilton Depression Rating Scale (r ¼ 0.25) (Beck et al., 1988).
The Inferential Confusion Questionnaire (ICQ; Aardema, O’Connor
et al., 2005) is a 15-item questionnaire measuring an overreliance
857
on imagination, a distrust of the senses, and a tendency to confuse
imagination with reality during reasoning. Items are rated on a 5point scale (1 ¼ strongly disagree to 5 ¼ strongly agree). The ICQ is
a unidimensional measure that has been found to explain a large
portion of the variance in symptoms of OCD even when controlling
for negative mood states and other cognitive domains (Aardema,
Radomsky, O’Connor, & Julien, 2008; Wu, Aardema, & O’Connor,
2009). As well, inferential confusion as measured by the ICQ is
related to treatment outcome independent of change in negative
mood states (Aardema, Emmelkamp et al., 2005). The scale
possesses good inter-item reliability (a ¼ 0.85).
The Inference Processes Task (IPT; Aardema et al., 2009) represents an ecologically valid analogue of OCD, which measures
doubting as an ongoing, dynamic process, rather than by one static
measurement. The IPT has previously been validated in a nonclinical and clinical sample and shown to have convergent validity with degree of obsessionality and measures of imaginative
involvement during reasoning (Aardema et al., 2009). At the
beginning of the task, the participant is presented with a written
scenario leading up to an inference of doubt that an accident might
have happened and that someone was hurt. Following the reading
of this scenario, the participant is asked to rate the probability that
an accident may have occurred on a scale from 10 to 100 (i.e. “What
do you consider to be the probability that an accident has happened
under these circumstances using the following scale?”). Higher
scores indicate a greater level of belief in the probability that an
accident might have occurred.
These initial scores are the baseline preceding subsequent
manipulations of level of doubt by introducing separate pairs of
reality and possibility-based information. Specifically, after rating
the probability concerning the occurrence of an accident, the
person is presented with a separate piece of reality-based information congruent with the idea that no accident had happened
(R1). Next, the participant is asked to turn the page and is presented
with a piece of possibility-based information (P1) that could
potentially negate the previous piece of reality based information.
And once again, the person is asked to rate the probability of an
accident having occurred. This process is repeated and the participant is presented with two additional pairs of reality and
possibility-based information (R2, P2, R3, P3).
The IPT produces a number of different variables related to
doubt formation and resolution during reasoning (see Aardema
et al., 2009). First, it produces a baseline level of doubt as the
result of reading the initial scenario. Second, it produces levels of
doubt at six different time points following baseline measurement
in the course of reasoning. Third, the task produces and separates
the impact of reality and possibility through calculating the
cumulative impact of reality and possibility on levels of doubt at the
appropriate time-points. And the final task measure is an end-point
level of doubt reflecting the extent the person is able to find
resolution to the doubt provoked by the scenario. A typical pattern
of reasoning as derived from the present data at pre-treatment is
represented in Fig. 1.
3. Results
3.1. Treatment effects on level of doubt and outcome measures
Treatment effects on the clinical outcome measures are represented in Table 1. Paired t-tests showed significant reductions in OC
symptoms as measured by the Y-BOCS and the PI. Effect sizes
(Cohen’s d) indicates an effectiveness similar to that found in an
earlier treatment outcome study using IBT (O’Connor, Aardema,
Bouthillier et al., 2005; O’Connor, Aardema, & Pélissier, 2005), as
well as effect sizes found in other cognitive-behavioural treatments
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Accident
858
80
70
60
No Accident
50
40
30
20
B
R1
P1
R2
P2
R3
P3
Fig. 1. Impact of reality (R1eR3) and negating possibility based information (P1eP3)
on level of doubt at pre-treatment (n ¼ 35).
for OCD (Abramowitz, 1998). In addition, levels of anxiety and
depression (BAI and BDI) improved significantly in the course of
treatment. There was also a significant reduction in level of inferential confusion as measured by the ICQ.
Pre- and post-treatment levels of doubt at the different time
points of the IPT are shown in Table 2. Paired t-tests showed
a significant reduction in levels of doubt at most of the different
time-points of the IPT after treatment. In addition, we calculated
the average impact of reality and possibility based information on
levels of doubt were found utilizing the same formulae as described
elsewhere (see Aardema et al., 2009):
Average Impact of Possibility Based Information
¼ ½ðP1 R1Þ þ ðP2 R2Þ þ ðP3 R3Þ=3
Average Impact of Reality Based Information
¼ 1*½ðR1 BÞ þ ðR2 P1Þ þ ðR3 P2Þ=3
Paired t-tests revealed significant reductions in the average impact
of reality and near significant reductions in possibility based
information on levels of doubt after treatment. This reduction was
expected in the impact of possibility based information. However,
a significant reduction was also observed in the impact of reality
based information, which was unexpected.
3.2. Treatment effects on the resolution of obsessional doubt
The primary objective of the current study was to establish
whether participants with OCD improved in their ability to resolve
obsessional doubt as defined by end-points levels of doubt. For the
current study, resolution was defined as a score of 20 or lower on
levels of doubt at the end-point of the IPT. This cut-off point
represents the lower range of scores on levels of doubt within one
standard deviation of mean scores reached by non-clinical participants at end-point (Aardema et al. M ¼ 32.37; SD 16.60;
range ¼ 10e100). Results on the ability of participants to find
resolution to doubt before and after treatment are represented in
Table 3.
The McNemar’s test, a nonparametric method for nominal data
to determine whether row and column marginal frequencies are
equal, indicated a highly significant difference in participants’
ability to resolve doubt as the result of treatment (p < 0.001).
Specifically, a substantially higher number of participants were able
to resolve doubt post-treatment (n ¼ 22) as compared to the
number of participants able to resolve doubt pre-treatment (n ¼ 8).
Yet, there remained a portion of participants who were not able to
resolve the doubt following treatment (n ¼ 13). Most of these
participants were also not able to resolve doubt pre-treatment
(n ¼ 12). Interestingly, perhaps the result of random error or
report bias, one person was able to resolve doubt before treatment,
but unable to do so following therapy.
On the basis of these results, we can identify the following
subgroups in our current sample for further analysis (n ¼ 34):
1) Resolution Group (n ¼ 15; 44.1%) -no resolution pre-treatment/
resolution post-treatment.
2) No Resolution Group (n ¼ 12; 35.3%) - no resolution pretreatment/no resolution post-treatment.
3) Pre-Resolution Group (n ¼ 7; 20.6%) - resolution pre-treatment/
resolution post-treatment.
3.3. The resolution of obsessional doubt and treatment outcome
The second aim of the present study was to establish whether
change in a person’s ability to resolve doubt is relevant to treatment
outcome. To investigate whether the effects of change in participants’ ability to resolve doubt was related to treatment outcome,
repeated measures ANOVAs were carried out with the outcome
measures as dependent variables and the previously identified
resolution subgroups as independent variables. Additional
repeated ANOVAs were run with change in baseline levels of doubt
added as a covariate. Means and standard deviations on measures
before and after treatment are represented in Table 4.
Baseline Differences in level of Doubt d Repeated ANOVA showed
an overall significant effect on baseline levels of doubt as measured
by the IPT (F (1, 31) ¼ 25.66; p < 0.001). However, none of the
groups improved more than the others on baseline levels of doubt
in the course of treatment (F (2, 31) ¼ 1.26; p ¼ 0.30). Nonetheless,
since changes in baseline levels of doubt may still attenuate results,
it was added as a covariate in supplementary analysis for each of
the different outcome variables.
Y-BOCS Total Score d Repeated ANOVA showed a significant
treatment effect with all groups improving in symptoms as
Table 1
Treatment effects on the clinical outcome measures (n ¼ 35).
Pre-treatment
Y-BOCS
Obsessions
Compulsions
PI
BAI
BDI
ICQ
Post-treatment
Mean
SD
Mean
SD
27.40
12.66
14.74
84.32
13.46
16.97
45.20
5.07
3.04
2.80
40.91
10.00
10.20
14.64
13.49
6.69
6.80
47.80
8.37
9.14
35.80
7.63
4.05
3.74
26.55
7.32
9.52
15.21
t
df
p
Cohen’s d
12.35
10.16
12.46
6.85
4.56
7.33
4.46
34
34
34
34
34
34
34
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
2.15
1.67
2.40
1.06
0.58
0.79
0.63
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859
Table 2
Treatment effects on levels of doubt and the average impact of possibility and reality during reasoning with the IPT (n ¼ 35).
Pre-treatment
Baseline
R1
P1
R2
P2
R3
P3
Cumulative average
impact of possibility
Cumulative average
impact of reality
Post-treatment
df
p
26.89
17.68
25.31
31.24
24.64
18.17
19.90
10.79
4.13
4.06
2.94
1.56
2.62
2.63
4.58
2.00
34
34
34
34
34
34
34
34
<0.001
<0.001
<0.01
0.13
<0.05
<0.05
<0.001
0.054
12.97
2.04
34
0.049
SD
Mean
SD
66.29
45.14
55.42
37.71
47.43
29.14
44.29
11.71
23.77
23.81
25.36
22.63
26.05
18.21
23.05
14.76
50.57
28.57
40.57
30.57
34.00
21.43
27.43
7.43
19.05
14.96
15.14
measured by the Y-BOCS total score (F (1, 31) ¼ 136.69; p < 0.001).
However, there was no significant treatment by group effect on the
Y-BOCS total score (F (2, 31) ¼ 1.58; p ¼ 0.22). These results did not
change when adding change in baseline levels of doubt as a covariate to the repeated ANOVA (F (2, 31) ¼ 1.53; p ¼ 0.23).
Y-BOCS Obsessions d There was an overall significant decrease
on the Y-BOCS obsessions subscale for all groups (F (1, 31) ¼ 98.47;
p < 0.001). As well, there was a significant treatment by group
effect with those in the Resolution Group improving more than any
of the other groups (F (2, 31) ¼ 3.37; p < 0.05). This result remained
significant when adding change in baseline levels of doubt as
a covariate (F(2, 31) ¼ 3.25; p ¼ 0.05).
Y-BOCS Compulsions d All groups decreased on the Y-BOCS
compulsions subscale (F (1, 31) ¼ 135.13; p < 0.001), but without
any interaction effects (F (2, 31) ¼ 0.58; p ¼ 0.56). Similar nonsignificant results were obtained for the interaction effect when
adding change in baseline levels of doubt as a covariate (F (2,
31) ¼ 0.42; p ¼ 0.66).
PI d There was a significant group effect with all the groups
improving in symptoms over time as measured by the PI (F (1,
31) ¼ 38.53; p < 0.001). In addition, there was a significant treatment by group effect with those in the Resolution Group improving
the most after treatment (F (2, 31) ¼ 3.34; p < 0.05). The interaction
effect remained significant when adding change in baseline levels
of doubt as a covariate (F [2, 31] ¼ 3.45; p < 0.05).
ICQ d There was an overall significant decrease in scores on the
ICQ following treatment (F (1, 31) ¼ 20.38; p < 0.001). As well, there
was a significant treatment by group effect with those in the
Resolution Group improving the most on inferential confusion (F (2,
31) ¼ 4.01; p < 0.05). This effect remained when adding change in
baseline levels of doubt as a covariate (F (2, 31) ¼ 4.03; p < 0.05).
BAI d All groups decreased on anxious mood (F (1, 31) ¼ 16.55;
p < 0.001) without any significant treatment by group effect (F (2,
32) ¼ 0.58; p < 0.57).
BDI d There was an overall treatment effect on depressive mood
as well with all groups improving (F (1, 31) ¼ 45.08; p < 0.001).
There was no significant interaction effect (F (2, 32) ¼ 0.39;
p < 0.68).
Table 3
Number of participants able to resolve doubt before and after treatment on the IPT
(n ¼ 35).
Post-treatment
Doubt unresolved
Post-treatment
Doubt resolved
Total
t
Mean
Pre-treatment
Pre-treatment
Total
Doubt unresolved
Doubt resolved
12
1
13
15
27
7
8
22
35
3.4. The role of reality and possibility in treatment outcome
The final aim of the study was to establish the separate contribution of reality and possibility in participants’ ability to resolve
obsessional doubt following treatment. Differences between the
subgroups before and after treatment were examined with
repeated measures ANOVAs. Also, additional ANOVAs were run in
order to control for change in baseline levels of doubt. Means and
standard deviations are represented in Table 5.
Impact of Possibility e There was an overall trend for the groups to
lessen in the impact of possibility following treatment (F (1, 31) ¼ 3.22;
p ¼ 0.08). In addition, there was a trend for the impact of possibility to
lessen more among those in the Pre-Resolution Group and Resolution
Group as compared to those in the No Resolution group (F (2,
31) ¼ 2.63; p ¼ 0.09). This effect did not appear due to changes in
baseline levels of doubt, which if added as a covariate to the repeated
ANOVA showed similar results (F (2, 31) ¼ 2.98; p ¼ 0.07).
Impact of Reality e There was a significant overall effect of impact
of reality for the groups as a whole (F (1, 31) ¼ 7.90; p < 0.01).
Participants were actually less impacted by reality based information following treatment. In addition, there was a trend towards
a group by treatment effect with those in Pre-Resolution Group and
Table 4
The resolution of obsessional doubt and treatment outcome (n ¼ 34).
Resolution group
No resolution
group
Pre-resolution
group
Mean
SD
Mean
SD
Mean
SD
25.13
25.60
79.17
67.50
13.79
17.12
55.71
28.57
28.78
25.13
4.61
6.19
27.21
16.17
5.01
7.62
28.86
13.29
6.36
9.84
2.01
3.23
11.83
7.83
3.41
4.00
13.43
7.00
4.20
5.66
3.08
3.07
15.50
8.33
2.31
3.84
15.43
6.29
2.37
4.27
33.28
22.50
83.83
58.25
45.75
22.50
49.29
25.71
26.47
19.84
6.71
14.20
46.17
43.67
15.93
12.80
31.29
20.14
10.74
6.59
4.90
4.85
18.00
12.33
14.70
9.94
6.71
3.86
4.27
2.91
9.81
9.40
20.00
10.75
11.88
11.74
14.00
6.71
8.64
5.96
Baseline level of doubt
Pre-treatment
62.00
Post-treatment
44.67
Y-BOCS total score
Pre-treatment
26.33
Post-treatment
11.00
Y-BOCS - obsessions
Pre-treatment
12.73
Post-treatment
5.47
Y-BOCS - compulsions
Pre-treatment
13.60
Post-treatment
5.53
PI
Pre-treatment
102.63
Post-treatment
51.07
ICQ
Pre-treatment
52.93
Post-treatment
38.20
BAI
Pre-treatment
13.20
Post-treatment
7.20
BDI
Pre-treatment
16.53
Post-treatment
9.40
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F. Aardema, K. O’Connor / J. Behav. Ther. & Exp. Psychiat. 43 (2012) 855e861
Table 5
Reality and possibility in the resolution of obsessional doubt (n ¼ 34).
Resolution SD
group
Impact of possibility
Pre-treatment 13.78
Post-treatment
4.00
Impact of reality
Pre-treatment 18.44
Post-treatment 13.56
SD
No
resolution
group
Pre-resolution SD
group
14.36 13.77
7.15 15.56
14.36
13.36
3.81
0.96
11.93
1.63
14.52 21.11
11.51 21.39
15.84 17.62
14.53
6.19
17.29
7.56
the Resolution group showing the greatest reductions in the impact
of reality (F (2, 31) ¼ 2.75; p < 0.08) . However, this trend turned
non-significant when adding change in baseline levels of doubt as
a covariate to the repeated ANOVA (F (2, 31) ¼ 1.62; p < 0.22).
4. Discussion
The current study investigated the pervasive nature of doubt in
OCD and its relationship to treatment outcome. Specifically, it was
expected that the participants’ ability to resolve obsessional doubt
would improve following IBT and that such improvements would
significantly relate to successful treatment outcome. The current
findings largely supported these hypotheses.
IBT produced notable changes in participants’ ability to reach
non-clinical levels of doubt. A significantly higher proportion of
individuals were able to resolve doubt post-treatment as compared
to pre-treatment (i.e. the Resolution Group). Even so, there
remained a proportion of individuals who were not able to find
resolution to the doubt provoked by the task even after treatment
(i.e. the No Resolution Group). In addition, a small proportion of
individuals was already able to resolve doubt before treatment, and
continued to do so after treatment (i.e. the Pre-Resolution Group).
Comparing the different groups at post-treatment, it was quite
clear that improvement in the ability to resolve doubt was positively
associated with treatment outcome. Specifically, lower levels of
obsessionality and negative mood states and inferential confusion at
post-treatment were most pronounced in the Resolution Group and
the Pre-Resolution group. This pattern was absent, however, with
respect to the clinician version of the Y-BOCS total score. Nonetheless,
a significant difference was observed in the Y-BOCS obsession
subscale, which is the primary target of IBT. Also, those who improved
in their ability to resolve obsessional doubt showed the greatest
reductions in inferential confusion - the reasoning process proposed
to be responsible for the perserverative nature of obsessional doubt.
Overall, in line with previous findings, IBT produced significant
reductions in levels of obsessionality, inferential confusion and
negative mood states. In addition, there were significant improvements in levels of doubt as measured by the IPT. Participants were
also less influenced by possibility based information introduced at
three different time-points in the task. Contrary to expectations,
however, there also was a significant reduction in the impact of
reality based information.
According to an inference based approach, obsessions obtain
their reality value from a high impact of possibility during
reasoning, which is why obsessions are so difficult to dismiss for
individuals with OCD. Reductions in the impact of possibility as the
result of treatment would therefore be considered to be beneficial
to those suffering from OCD. However, the current task also showed
significant reductions in the impact of reality based information
during treatment, which was unexpected. This appears to suggest
that change in the impact of reality is relevant to improvements in
the resolution of doubt. However, these results pertain to the group
as a whole, which is quite heterogeneous in terms of their ability to
resolve doubt, both before and after treatment. Looking at the
groups separately, change in the impact of reality did not significantly differentiate between those who improved in their ability to
resolve to doubt and those who did not. In contrast, a trend was
observed where change in the impact of possibility did differentiate
between different groups.
One explanation for the lessened impact of reality following
treatment might be that people with OCD simply become more
confident as the result of treatment, less likely to be influenced by
outside influences or information regardless of whether it is reality
or possibility based. Another explanation might be that the lessened
impact of reality following treatment was due to test-retest effects
and familiarity with the task. The result is a lowered impact of both
possibility and reality based information. This also highlights an
important limitation of the current study, which is that there was no
control for test-retest effects. It might be useful to add a natural
waiting list control group to control for such effects in future studies.
Other important limitations of the present study are relatively
small sample sizes preventing more powerful multiple comparisons between groups as well as the inclusion of additional control
variables such as change in anxiety and depression. Nonetheless,
the current study did clearly show that the ability to resolve
obsessional doubt is closely linked to the most relevant quantifiers
of treatment outcome. These results held when controlling for
baseline change in level of doubt. In addition, a trend was found
where a reduction in the impact of possibility based information
was most pronounced among those who improved in their ability
to resolve doubt. A similar trend was observed in the impact of
reality, but became non-significant when controlling for baseline
levels of doubt. We can therefore conclude change in the impact of
possibility is likely still the more important variable to consider in
alleviating obsessional doubt.
In conclusion, the current study showed that the ability to resolve
obsessional doubt is an important process to consider in treatment,
and may be successfully targeted with IBT in a significant proportion
of participants. Clearly, however, the current study is only a first step
in the experimental measurement of inferential confusion and its
relationship to treatment outcome. Causal interpretations on the
basis of current results would be premature. In particular, the current
study would benefit from replication, controls for test-retest effect,
and investigation in larger samples. Nonetheless, results represent
a further step in highlighting a key role for doubt in OCD and its
operationalization in reasoning about possibility.
Acknowledgements
The study was in part supported by a grant (no. 111261) to the
first author from the Canadian Institutes for Health Research (CIHR).
The first author is also a recipient of the CIHR New Investigator
Award and an additional research scholar award from the Quebec
Health Research Fund (Fonds de la recherche en santé du Québec).
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