Figure 3: Number of recovered, improved, unchanged, and deteriorated patients at the end of therapy based on the Reliable Change Index classification (RCI) in both trauma groups. Error bars represent standard deviations between the imputed data sets. Most patients recovered, with no significant differences between the trauma groups.

Differences between the Depression Groups

According to Hypothesis 2c, we tested for differences in the effect of trauma on symptom severity over time between patients diagnosed with and without a depression disorder.
For the BAI, adding the depression factor did not improve the model (F (1, 2,723.98) < 0.01, p = .986), neither did the interaction effect between depression and trauma (F (1, 2,975.45) = 0.73, p = .393), depression and time point (F (1, 723.22) = 0.75, p = .388) or depression, trauma and time point (F (1, 937.24) = 0.27, p = .606). Results indicate no differences in the BAI scores or trajectories and no differences in the effect of the trauma group on BAI scores between the depression groups; see also Supplemental Figure 6.
For the BDI-II, adding the depression factor (F (1, 1,633.38) = 22.27, p < .001) significantly improved the model, but adding the interaction effect between depression and trauma (F (1, 4,536.77) = 0.21, p = .645) and between depression, trauma and time point (F (1, 1,106.90) = 0.47, p = .494) did not, indicating no evidence for differences in the effect of the trauma group on BDI-II scores between the depression groups. More detailed information on the effects of depression over time on BDI-II scores is given in the Supplemental Material.

Differences between the Trauma Subtypes

Differences in the impact of interpersonal, non-interpersonal, and no trauma on symptom severity over time were tested according to Hypothesis 3 using the interpersonal trauma index instead of the global trauma index. Adding the interpersonal trauma factor did not improve the models for anxiety and depression symptoms (BAI: F (2, 542.09) = 1.92,p = .148, BDI-II: F (2, 1,503.24) = 2.69, p = .068), nor did the interaction effect between interpersonal trauma and time point (BAI: F (2, 237.55) = 1.15, p = .319, BDI-II:F (2, 490.63) = 1.38, p = .254), indicating no differences in symptom severity or trajectories between patients with interpersonal trauma, non-interpersonal trauma only and no trauma, see Supplemental Figure 7.

Effects of Trauma-specific Interventions

In an exploratory analysis in line with the not preregistered Hypothesis 4, adding the factor trauma-specific intervention (none or at least one) did not improve the model for depression or anxiety severity (BAI:F (1, 4,936.26) = 0.27, p = .602, BDI-II: F (1, 3,584.34) = 0.01, p = .931), neither did adding the interaction effect between trauma-specific intervention and trauma (BAI: F (1, 6,180.62) = 0.69, p = .405, BDI-II: F (1, 4,754.02) = 0.01,p = .943), trauma-specific intervention and time point (BAI:F (1, 1,123.00) = 0.24, p = .624, BDI-II: F (1, 1,311.98) = 3.13, p = .077) or trauma-specific intervention, trauma and time point (BAI: F (1, 979.65) = 0.73, p = .392, BDI-II: F (1, 1,388.50) < 0.01, p = .995). This indicates no significant differences between groups with and without trauma-specific intervention in the overall symptom severity and the decrease in symptom severity, regardless of trauma history, see Figure 4.