Discussion
There was a significant posttreatment change in several belief
dimensions for both the APC and CBT groups, including
Strength of Belief, Preoccupation With Belief, Systematization
of Belief, Affect Relating to the Belief, and Idiosyncrasy
of Belief The most significant change in both groups lay in an
increased ability to control actions and communications
related to the belief However, in accordance with expectations,
the benefit of CBT was supported by significant
group-by-treatment interaction effects for the following
items: "subjective strength of conviction," "idiosyncratic distress,"
"reactions to beliefs," and "stopping acting on beliefs."
Available questionnaire data supported the clinical outcome
findings (see Table 3), with CBT showing improved outcomes
on depression and self-esteem.
Previous studies have reported on improvements unique to
CBT but also have stated that these benefits are sometimes
minimal when compared with other active psychological
treatments.'^ Clinical outcome status in the present study was
categorized according to degree and type of improvement on
the MADS subscales, and the current results also support a
low (0.16) to medium (0.28) effect size between APC and
CBT (depending on the measure). These results provided
posterior power (a = .05) of between 0.30 and 0.60 for the
main hypothesized (between-treatment) effect, whereas the
much stronger main treatment effect size of 0.3 to 0.6 yielded
power estimates between 0.4 and 0.95, regardless of intervention
modality. Since the clinical outcome measures are concordant,
the results are clearly robust. The posttreatment
decrease in the "strength of belief parameters was 40% in
CBT and 28% in APC. Neither therapy succeeded overall in
reducing the Strength of Conviction score to zero. However,
in one patient treated with CBT, the item "strength of belief
dropped to zero, and in 2 others. Preoccupation With Belief
score dropped to zero. The changes in questionnaire results
showed robust effect sizes, particularly for those measuring
depression and self-esteem, even though data were only available
on a smaller number of completers. The low-to-moderate
effect sizes for comparisons between the CBT and APC may
be due to large individual variation in response to treatment
among participants. Altematively, establishing a strong positive
rapport can affect scores on Insight, Preoccupation With
Belief, and Affect Relating to Belief.' In contrast to hallucinations,
a minimum of directive intervention in the form of
befriending, social support or supportive counselling, and
unstructured treatments may influence delusions.^