TABLE 2.
Corrected mixed‐regression based estimated means and standard errors (SE)
| Pre‐ | Post‐ | Cohen's d | |||||
|---|---|---|---|---|---|---|---|
| Group | Mean | SE | Mean | SE | Within‐group | Between‐group | |
| Log‐transformed | IRT | 1.44 | 0.08 | 0.87 | 0.13 | 1.11 | 1.03* |
| Nightmare frequency | WL | 1.53 | 0.09 | 1.49 | 0.12 | 0.08 | |
| Nights with nightmares | IRT | 3.16 | 0.27 | 1.71 | 0.32 | 0.88 | 0.76ns a |
| WL | 3.33 | 0.27 | 3.13 | 0.32 | 0.12 | ||
| Nightmare distress (NDIQ) | IRT | 20.43 | 0.80 | 11.49 | 1.63 | 1.87 | 0.75* |
| WL | 20.33 | 0.81 | 14.96 | 1.59 | 1.12 | ||
| Mastery | IRT | 11.86 | 3.18 | 51.47 | 4.82 | −2.10 | −1.77*** |
| WL | 11.97 | 3.24 | 18.17 | 4.78 | −0.33 | ||
| Depressive symptoms (PHQ) | IRT | 8.98 | 0.79 | 6.64 | 0.79 | 0.50 | 0.30ns |
| WL | 9.29 | 0.81 | 8.33 | 0.77 | 0.21 | ||
| Anxiety (HADS‐A) | IRT | 7.65 | 0.62 | 7.10 | 0.73 | 0.15 | 0.19ns |
| WL | 7.09 | 0.63 | 7.25 | 0.70 | −0.04 | ||
| Insomnia severity (ISI) | IRT | 15.09 | 0.72 | 10.45 | 0.88 | 1.07 | 1.12*** |
| WL | 14.79 | 0.73 | 15.03 | 0.84 | −0.06 | ||
d within = (M pre − M post)/SD pooled‐pre; d between = [(M preIR − M postIR) − (M preWL − M postWL)]/SD pooled‐pre; means for effect size calculations were based on mixed‐regression based estimated means; SDs for effect size calculations were based on the observed values.
Abbreviations: HADS‐A, Hospital Anxiety and Depression Scale‐Anxiety; IRT, imagery rehearsal therapy; ISI, Insomnia Severity Index; NDIQ, Nightmare Distress and Impact Questionnaire; PHQ, Patient Health Questionnaire; WL, wait‐list.
a
Pre‐post analyses were significant (F 1,62.20 = 5.97, p = .017, d = 0.71).
*
p < .05; *** p < .001.