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HYPNOTIC ANALGESIA IN PERSONS WITH DISABILITIES
213
Thus, hypnotizability data were available for 31 (94%) of the study
participants.
Treatment-outcome expectancy was assessed with the 4-item Treat-
ment Expectancy Scale (TES; Holt & Heimberg, 1990), with the TES
items modified to address the treatment of pain. The items of the TES
used in this study begin with the stem, “You will receive 10 sessions of
a treatment for pain. Based on what you have heard about the treat-
ment so far
. . .
” Participants were then asked to rate the perceived logic
of (“How logical does this type of treatment seem to you?”) and their
confidence in the treatment for themselves (“How confident would
you be that this treatment will be successful in eliminating your pain?”
and “How successful do you feel this treatment will be in decreasing
your pain?”) and for others (“How confident would you be in recom-
mending this treatment to a friend who was experiencing a great deal
of pain?”) on 0 to 10 numerical scales. Participants were asked to
respond to these items at the beginning of the first session (before they
had a chance to experience the treatment protocol for the first time)
and at the very end of the first session, because we anticipated that
experience with hypnotic treatment might alter expectancies.
Responses to the four TES items were averaged to form two (preses-
sion and postsession) treatment-outcome expectancy composite scores.
The original version of the TES has been used successfully to compare
the reliability of control treatments in treatment-outcome research
(cf. Heimberg, Dodge, Hope, Kennedy, & Zollo, 1990) and to deter-
mine the extent to which treatment credibility predicts treatment out-
come (Chambless, Tran, & Glass, 1997; Safren, 1997).
Data Analysis
The primary study question, the change in pain intensity that can be
expected following hypnotic-analgesia treatment, was addressed
statistically in three ways. First, the impact of the hypnotic-analgesia
intervention (relative to a no-treatment baseline period) was examined
in the intent-to-treat (
n
= 30) and efficacy analysis (
n
= 26) samples
using repeated measures analyses of variance (ANOVAs), with aver-
age pain intensity as the dependent variable and time (prebaseline,
postbaseline/pretreatment, posttreatment, 3-month follow-up) as the
independent variable. Significant time effects, if they emerged, were
followed up with univariate tests to identify the point(s) at which pain
intensity changed over the course of the study period. Second, effect
sizes (
d
, Cohen, 1988) were computed for the pretreatment to posttreat-
ment change in pain to determine the relative size of the effect of treat-
ment. Finally, because findings concerning average change in pain
intensity across the study participants does not provide information
concerning the rates of positive response in the sample (a moderate
average change in pain for the sample as a whole could be obtained,