Initial treatment outcome
The primary analysis in this study is the comparison of CAPS scores for the two conditions from pre-treatment to post-treatment. The relevant mean scores are in Table
2 along with the means for the CBT condition available for the 3-month follow-up.
Table 2
Pre-treatment and post-treatment CAPS scores on all groups and 3-months follow-up CAPS scores on treated groups
CBT |
M | 47.6 | 18.3 | 18.9 |
SD | 19.1 | 18.8 | 23.8 |
Wait List |
M | 41.8 | 35.2 | - |
SD | 17.1 | 23.0 | - |
A repeated measures ANOVA (Group × Time) revealed a significant main effect of Time (F [1, 40] = 63.79, p < 0.001, Cohen's d = 2.53) and a significant interaction of Group × Time (F [1, 40] = 25.81, p < 0.001, d = 1.61) but no main effect of Group. A between group comparison at post-test by ANCOVA (controlled for pre-values) revealed that the CBT condition showed greater PTSD symptom reduction than WLC (F [1, 39] = 23.47, p < 0.001, d = 1.55).
The intent-to-treat analysis including data from drop-outs revealed similar results, a main significant effect of Time (F [1, 42] = 51.0, p < 0.001, d = 2.20) and a significant interaction of Group × Time (F [1, 42] = 18.9, p < 0.001, d = 1.34). For controlling the gender imbalance of the two groups a repeated measures ANOVA (Group × Time) was performed only for women (19 in CBT and 13 in WLC) and revealed an even higher significant main effect of Time (F [1, 30] = 83.02, p < 0.001, Cohen's d = 3.33) and a significant interaction of Group × Time (F [1, 30] = 33.69, p < 0.001, d = 2.12) but no main effect of Group.
A second way to view these data is in terms of the categorical variable of whether participants changed diagnostic category or improved from PTSD/subsyndromal PTSD to non-PTSD. This could also be seen as a measure of clinically significant change. The categorical diagnostic data from before to after treatment are shown in Table
3.
Table 3
Clinical significance: Categorical diagnostic results for PTSD before and after treatment
CBT (N = 21) | PTSD (N = 12) | PTSD (N = 3) | PTSD (N = 4) |
| | Sub-PTSD (N = 2) | Sub-PTSD (N = 1) |
| | Non-PTSD (N = 7) | Non-PTSD (N = 7) |
| Sub-PTSD (N = 9) | PTSD (N = 0) | PTSD (N = 0) |
| | Sub-PTSD (N = 2) | Sub-PTSD (N = 0) |
| | Non-PTSD (N = 7) | Non-PTSD (N = 9) |
Wait List (N = 21) | PTSD (N = 10) | PTSD (N = 6) | - |
| | Sub-PTSD (N = 3) | - |
| | Non-PTSD (N = 1) | - |
| Sub-PTSD (N = 11) | PTSD (N = 2) | - |
| | Sub-PTSD (N = 6) | - |
| | Non-PTSD (N = 3) | - |
These data were analyzed with a 2 × 2 chi square test comparing status of full recovery (non-PTSD) in the CBT or control condition. It revealed that CBT was superior to Wait List (Chi2 [1, N = 21] = 3.70, p < 0.05) post-treatment. Thus, in summary 67% of those with initial PTSD or sub-PTSD treated by CBT had improved, compared to 19% of those on the Wait List who were assessed twice.
Our assessments allowed us to examine possible changes in co-morbid major depressive disorder (MDD). It should be remembered that this co-morbid condition was not explicitly targeted by the treatment. Results for MDD were: Seven patients from CBT condition had MDD prior to treatment, all recovered from MDD at post-treatment. Three patients from WLC condition had MDD prior, 2 cases remained depressed by the post-treatment assessment. Chi squares test revealed, for those with MDD (49% of the sample), that CBT led to a significantly higher rate of recovery than Wait List (Chi2 [1, N = 21] = 5.74, p < 0.05). Moreover, none of the participants in the CBT condition who were not depressed initially became depressed during treatment.
Psychological questionnaires
Table
4 lists the pre-treatment and post-treatment values for each of the psychological tests (in the interest of brevity the 3-month follow-up values for the CBT participants are also listed). Also in the table there are (a) results for the Group × Time interaction from the Group × Time repeated measures MANOVA and (b) whether the within group change is significant from pre-treatment to post-treatment (and from post-treatment to 3-month follow-up).
Table 4
Psychological test results for all groups at pre-treatment, post-treatment and 3-months follow up
IESR-Intrusion | Pre | 21.7a
| 20.0a
| F = 28.5, p < 0.001 | F = 28.8, p < 0.001, |
| Post | 7.6b
| 17.6a
| d = 1.89 | d = 1.74 |
| FU | 8.8b
| - | | |
IESR-Avoidance | Pre | 19.0a
| 16.5a
| F = 10.7, p < 0.01 | F = 10.4, p < 0.01 |
| Post | 10.7a
| 16.6a
| d = 1.16 | d = 1.05 |
| FU | 8.8a
| - | | |
IESR-Hyperarousal | Pre | 20.1a
| 20.7a
| F = 11.9 p < 0.001 | F = 8.9, p < 0.01 |
| Post | 9.6b
| 16.6a
| d = 1.22 | d = 0.97 |
| FU | 9.2b
| - | | |
BDI | Pre | 17.9a
| 16.0a
| F = 4.9 p < 0.05 | F = 6.6, p = 0.14 |
| Post | 9.1b
| 12.6a
| d = 0.78 | d = 0.83 |
| FU | 10.0b
| - | | |
STAI | Pre | 50.5a
| 49.1a
| F = 6.4 p < 0.01 | F = 6.5, p < 0.01 |
| Post | 40.9a
| 46.2a
| d = 0.89 | d = 0.83 |
| FU | 41.9a
| - | | |
PTCI | Pre | 123.3a
| 107.9a
| F = 20.2 p < 0.001 | F = 16.7, p < 0.001 |
| Post | 86.1b
| 100.25a
| d = 1.59 | d = 1.33 |
| FU | 92.5b
| - | | |
Examining the results in Table
4 one finds significant (all p < 0.01) change for those receiving CBT on measures of intrusive and avoidance symptoms, depressive symptoms (BDI), and posttraumatic cognitions (PTCI) from pre-treatment to post-treatment with no additional change in follow-up. Those in the Wait List condition did not significantly change on any measure. Between group comparisons at post-test by ANCOVAs (last column of table
4) revealed that the CBT condition showed greater change than WLC (all p < 0.01).
Three-month follow-up outcome
For the 3-month follow-up, data of only n = 17 participants were available due to logistic problems of the research project. A series of repeated measure MANOVAs showed stability of measured psychopathology (see superscripts in table
4).
Table
2 already showed the mean CAPS scores at follow-up. Because of the lack of untreated control condition only tests of stability of treatment success in the CBT condition are available (paired t-test
post/FU(16) = 0.7, p = 0.52). From post-treatment to follow-up, the recovery rate (i.e. rate of non-PTSD, see table
3) increased slightly from 67% to 76% of the initial CBT group.