Comparison of results

Additional analyses were conducted with data from both studies taken together for materials and questionnaires applied in Study 1 as well as in Study 2 (STAI-S and STAI-T, LSAS, FNE-S, Interpretation Questionnaire for Social Phobia, and general and social scenarios of the interpretation experiment). The results will be reported below. In addition, results from the separate data analyses already reported in sections 6.2 and 7.2 will be referred to each other.

Taken together, both studies yielded comparable results even though they were conducted in two different languages with purely language-based material.

Study 1 compared panic disorder subjects, social phobia subjects, and control subjects. A number of participants from the two clinical groups fulfilled criteria for up to two additional current and/or past disorders. Social phobia subjects were about twice as affected from comorbidity than panic disorder subjects (see Table 6.3). Study 2 compared social phobia subjects, depressed subjects, and control subjects. In the two clinical groups, only participants without an additional disorder (with the exception of a current specific phobia or an emotional disorder more than 2 years in the past) were included in Study 2. Therefore, the social phobia group of Study 1 displayed the greatest pathology.

Subjects of the social phobia group from Study 1 scored highest on all four questionnaires presented to participants of both studies (LSAS, FNE-S, STAI-T and SSTAI-TAI-S) as well as on the two subscales of the LSAS (fear and avoidance).

Their sum scores differed significantly from all common sum scores of the social phobia group from Study 2 (all t≥2.6; p≤.011).

Except for the STAI scores, the social phobia group of Study 1 also differed significantly from the depression group of Study 2 (all t≥2.9; p≤.006), and from the panic disorder group of Study 1 in the LSAS and its subscales, the FNE-S and the STAI-S (all t≥2.7; p≤.01). In the trait and state versions of the STAI, the social phobia group of Study 1 reached scores identical to the depression group of Study 2, pointing to the strong negative affect present in the social phobia group of Study 1.

The two control groups, on the other hand, were very much alike. The control subjects of Study 1 and Study 2 only differed significantly on the fear subscale of the LSAS (t=2.4; p=.018) where the control group of Study 1 scored somewhat higher than the control group of Study 2, and on the STAI-S (t=2.6;

p=.011), with participants from Study 2 being slightly more fearful than participants from Study 1.

The overall pattern of results in the two studies was identical. The findings from the two methods, interpretation questionnaire and interpretation experiment, will be discussed separately below.

8.1.1 Interpretation questionnaires

In the interpretation questionnaires, there was no clear evidence for a disorder-specific bias favoring threatening or dysfunctional interpretations over non-threatening, functional ones in social phobia, panic disorder or depression.

Rather, clinical subjects evaluated the probability of threatening/dysfunctional and non-threatening/functional interpretations of ambiguous events very much alike, while control subjects displayed a clear preference for non-threatening and functional interpretations. With one exception, the difference between the two scale means (non-threatening/dysfunctional minus threatening/functional interpretations) was always ≤|1| for clinical groups and >1 for control groups.

Only in the Interpretation Questionnaire for Depression (IQD) did Study 2 social phobia subjects also achieve a difference >1, displaying a strong bias for functional interpretations. However, this interpretation questionnaire differs to some extent from the other interpretation questionnaires for anxiety, making direct comparison slightly difficult. In the IQD, functional interpretations seem more likely to all participants, even depressed ones.

On all scales of the interpretation questionnaires presented in Study 1 and Study 2, the only significant bias for threatening interpretations was found in Study 1 social phobia subjects, displaying the hypothesized disorder-specific negative interpretive bias (Mbias=–0.8). However, as summarized above, the difference of the probability ratings between threatening and non-threatening interpretations was again <1.

Pearson bivariate correlation between the LSAS and the social bias of the interpretation questionnaire was highly significant (all p<.001; rrStudy 1=–.87; rrStudy 2=–.71; rrboth=–.78). Partialling out participants' depression using their BDI or FDD score (Study 1 or Study 2 resp.), partial correlation between the social bias and the LSAS score were reduced, but remained highly significant (all p<.001; rrStudy 1=–

.79; rrStudy 2=–.59). Apparently, social phobia patients may display a cognitive bias for threatening interpretations of ambiguous social situations if their disorder is impairing enough (LSAS>80) while depression only adds to the overall psychopathology.

Compared to control subjects, clinical subjects were significantly more likely to think of threatening/dysfunctional interpretations and significantly less likely to think of non-threatening/functional interpretations of all types of ambiguous situations. Significant differences between clinical groups only appeared on disorder-specific threatening subscales (panic-threatening and

social-threatening in Study 1, depression-dysfunctional in Study 2). Thus, beyond a general tendency of clinical participants to rate the probability of threatening/dysfunctional interpretations higher and of non-threatening/functional interpretations lower than healthy control subjects, there is an added disorder-specific negativity endorsing threatening or dysfunctional interpretations of disorder-relevant situations more strongly (as “possible to likely”).

8.1.2 Interpretation Experiment

In both studies, the interpretation experiment did not provide any evidence for differences in interpretive processes of clinical and control groups. The interaction between the two factors “group” and “cue condition” never reached statistical significance. Although there was some variation between groups under the different situational conditions (unspecific, panic-relevant, social, and depression-relevant scenarios), the conservative view that all experimental groups were void of any systematic interpretation bias seems most appropriate. Generally, comprehension time differences under the “no cue” condition lay somewhere between the differences under the two cued conditions “threat cue” and “non-threat cue.” Contrast analysis usually supported at least two different models for the data, with the model “no bias” always being among them.

In addition, disorder-specific scenarios (panic-relevant, depression-relevant, social) posed a serious problem. The necessary assumption that continuation sentences were interpreted differently under the cue conditions

“threat” and ”non-threat” was not fulfilled for at least one of the experimental groups. Therefore, further interpretation of results for disorder-relevant ambiguous situations was not possible.

In order to replicate the results of the original study by MacLeod and Cohen (1993) who had developed the comprehension paradigm, participants of Study 1 and Study 2 were regrouped into the original STAI-T based high and low trait anxious groups, applying the same score limits that the authors had used. All other subjects were excluded from this analysis and only unspecific scenarios were reanalyzed. Unfortunately, this post-hoc procedure resulted in very low subject numbers in Study 1 (nlow=13 and nhigh=9). Overall, results from MacLeod and Cohen could not be replicated in either of the two studies. The interaction between the two factors “group” and “cue condition” did not reach statistical significance.

In Study 1, comprehension time differences under the cue condition “no cue” lay about equidistant between comprehension time differences under the two conditions

“threat cue” and “non-threat cue,” suggesting no interpretive bias at all.

In Study 2, with sufficient subject numbers (nlow=44 and nhigh=24), within-group t-tests revealed the expected differences: a bias for non-threatening interpretations in low trait anxious subjects and a bias for threatening interpretations

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Speeding on threat continuations (in milliseconds)

threat cue no cue non-threat cue Cue condition

l o w t r a i t a n x i o u s s u b j e c t s h i g h t r a i t a n x i o u s s u b j e c t s

in high-trait anxious subjects. However, analyses of data from both studies together, attempting to increase power, still did not provide significant interaction between the factors “group” and “cue condition” (F<1; n.s.). Figure 8.1 shows the relative speeding on threat continuation sentences of unspecific scenarios for low and high trait anxious subjects based on data from Study 1 and Study 2 analyzed together.

Within-group comparisons of the comprehension time differences under the three cue conditions yielded results similar to Study 2: low trait anxious subjects displayed a bias for non-threatening interpretations of ambiguous unspecific scenarios (“no cue” vs. “threat cue”: t(56)=2.80; p=.007; “no cue” vs. “non-threat cue”: t(56)=1.76; n.s.), while high trait anxious subjects were biased toward threatening interpretations (“no cue” vs. “threat cue”: t(33)=1.15; n.s.; “no cue” vs.

“non-threat cue”: t(33)=2.67; p=.012). Between groups, the differences under the

“no cue” condition were not significantly different from each other (t(88)<1; n.s.).

Taken together, the safest and most conservative interpretation of results is the absence of a definite interpretive bias in the two original STAI-T groups, possibly because analysis was based on too few scenarios.

Figure 8.1: Relative speeding on threat continuation sentences of unspecific scenarios for low and high trait anxious groups in both studies together

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Speeding on threat continuations (in milliseconds)

threat cue no cue non-threat cue Cue condition

2nd Quartile 4 t h Q u a r t i l e

1 s t Q u a r t i l e 3 r d Q u a r t i l e

Because Study 1 and Study 2 investigated clinical groups while MacLeod and Cohen (1993) had only worked with undiagnosed university students, the range of the STAI-T sum score was considerably smaller in the original groups.

Therefore, to extend MacLeod and Cohen's findings, participants in Study 1 and Study 2 were divided into four STAI-T based groups, applying percentile limits, and unspecific scenarios were analyzed again. The results of Study 1 and Study 2 were unexpected, yet almost identical: subjects with very high trait anxiety (4^th Quartile) displayed a bias for non-threatening interpretations of ambiguous unspecific scenarios. Analysis of both data sets together yielded a significant interaction of the two factors ”group” and “cue condition” (F(6,346)=2.31; p=.034).

Apparently, with enough power, the marginal significance of Study 2 turns into significant differences in interpretation among the four STAI-T groups. Figure 8.2 shows the relative speeding on threat continuation sentences of unspecific scenarios for STAI-T based groups of Study 1 and Study 2 analyzed together.

Figure 8.2: Relative speeding on threat continuation sentences of unspecific scenarios after recoding subjects of both studies into four STAI-T groups

Within-group comparisons consolidated the findings of Study 2: very low trait anxious subjects (1^st Quartile) displayed no interpretive bias at all, comprehension time differences under the “no cue” condition lay equidistant between the differences under the two cued conditions (“no cue” vs. ”threat cue”:

t(24)=2.53; p=.018; “no cue” vs. “non-threat cue”: t(24)=2.14; p=.043). Low trait

anxious subjects (2^nd Quartile) preferred non-threatening interpretations of ambiguous unspecific scenarios as they interpreted uncued ambiguous sentences in the same way as non-threat-cued ambiguous sentences (“no cue” vs. “threat cue”:

t(31)=2.41; p=.022; “no cue” vs. “non-threat cue”: t(31)<1; n.s.). High trait anxious subjects (3^rd Quartile), on the other hand, showed a strong bias for threatening interpretations of ambiguous unspecific scenarios (“no cue” vs. “threat cue”:

t(33)<1; n.s.; “no cue” vs. “non-threat cue”: t(33)=4.37; p<.001). Finally, very high trait anxious subjects also displayed a strong bias in the opposite direction, they comprehended uncued ambiguous unspecific scenarios in the same way as non-threat-cued ambiguous scenarios (“no cue” vs. “threat cue”: t(85)=3.68; p<.001; “no cue” vs. “non-threat cue”: t(85)=1.22; n.s.). Consequently, significant differences between groups were found for comprehension times under the “no cue” condition for the 2^nd and 4^th Quartile vs. the 3^rd Quartile (both t≥2.10; p≤.037), underlining the opposite interpretational directions of these groups.

8.2 Evaluation of the interpretation questionnaires