Discussion

Trauma history in patients with anxiety or depressive disorders may hinder the effects of psychological treatments. We investigated the effects of trauma on the duration of therapy, applied interventions, and symptom severity in outpatients receiving naturalistic CBT. Circa half of the 340 outpatients were classified as having experienced trauma, and in 79 cases (45.66% of all trauma cases), therapists applied a trauma-specific intervention.
General treatment characteristics like the number of sessions and the use of trauma-specific interventions, except for skills training, did not differ between the groups, indicating that CBT was delivered similarly to all patients, regardless of trauma history. The overall severity of depression as well as anxiety was higher among patients with a trauma history, in line with prior findings (Chu et al., 2013; Fullana et al., 2019; Hovens et al., 2015; Kuzminskaite et al., 2021; Mandelli et al., 2015; Nelson et al., 2017). The reduction in symptom severity throughout treatment and recovery rates were comparable between patients with and without a trauma history. For anxiety symptoms, this is mainly in line with the existing literature (Bruce et al., 2013; Trautmann et al., 2019), while for depressive symptoms, prior studies reported lower success of a variety of treatments in patients with a trauma history (Fischer et al., 2018; Miniati et al., 2010; Nanni et al., 2012; Serbanescu et al., 2020). Previous studies, however, did not investigate CBT treatments specifically and focused mainly on childhood interpersonal trauma. Studies showing reduced response to CBT were conducted mainly in depressed adolescents (Lewis et al., 2010; Waldron, Howard, & Reinecke, 2019). Differences in the investigated psychotherapy type and patient age might have contributed to the diverging results. Our findings are, however, consistent with the results of a recently published meta-analysis on the effects of childhood trauma across both pharmacological treatment and psychotherapy, concluding that evidence-based treatments for depression are similarly effective for patients with and without a history of childhood trauma (Kuzminskaite et al., 2022).
To our knowledge, this study is the first to investigates the effects of trauma history under naturalistic treatment conditions. In addition to the longer treatment duration (on average 44 sessions) in our study compared to the abovementioned studies (i.e., less than 20 sessions), therapists were free to choose therapeutic interventions for each patient, offering possibilities for personalized treatment. Our results indicate that among the assessed interventions, therapists independently from the trauma group most often applied interventions focusing on the regulation of extreme emotions and coping with maladaptive cognitive-emotional schemata (schema mode interventions, self-calming techniques, and skills training) compared to trauma-focused interventions. However, except for skills training, we did not find evidence for a specific use of these interventions in patients with a trauma history. The criteria on which therapists based their choice of trauma-specific interventions remained unclear. The decision may have been more bound to the therapist’s therapeutic style rather than the patient’s characteristics 11Exploratory analyses revealed significant differences between the therapists in intervention use irrespective of the patient, \(\chi^{2}\)(59) = 93.76, p = .003. Therapists, who treated at least 5 different patients, used a trauma-specific intervention for between 0.00% and 85.71% of their patients.. Although trauma-related treatments were not necessarily applied more frequently in patients with a trauma history, exploratory analyses revealed no differences in symptom severity trajectories between patients who did or did not receive trauma-specific interventions, regardless of trauma history. Thus, we did not find evidence for an efficient personalization of the therapy content based on the patient’s trauma history. These explorative analyses also suggest that trauma-specific interventions did not boot symptom reduction in those patients with an initial higher symptom severity.
While prior studies found more severe long-term consequences of interpersonal than non-interpersonal trauma (Bridges-Curry & Newton, 2021; Contractor et al., 2018), we did not find any effects when comparing the interpersonal, non-interpersonal, and no-trauma groups. This might be due to the relatively small sample size in the non-interpersonal trauma group (n = 12, 23.12%) and considerable heterogeneity in the symptom severity trajectories in this group, see Supplemental Figure 7. As a result of low subgroup sample size and high within-group variance, we may not have been able to detect between-group differences. The same might have been accurate for comparing patients with and without a depression diagnosis as the latter group was comparatively small (n = 46, 13.53%).
The current study sheds light on applied interventions and treatment trajectories in naturalistic CBT for depressed or anxious outpatients. It thereby extends evidence from well-controlled therapy trials by investigating CBT under routine care conditions. Furthermore, the data collection from archive files rules out any effects of the scientific investigation on treatment implementation or results. On the downside, therapy files did not always provide sufficiently detailed information. Childhood trauma was assessed through clinical routine data only, and therapists seldom used validated diagnostic tools to assess trauma history. Although retrospective trauma assessment is generally reliable (Kendall-Tackett & Becker-Blease, 2004), it tends to underestimate childhood trauma (Hardt & Rutter, 2004), especially in clinical records (Rossiter et al., 2015). Our study might, therefore, have underestimated the amount of childhood trauma. Furthermore, although interrater reliability was sufficient for trauma and intervention indices, single trauma subtypes had low reliabilities and did not allow further analyses to differentiate the effects of single trauma subtypes. Also, the effects of childhood and adulthood interpersonal trauma were not separable because both groups had extreme overlap. Future studies should encourage therapists to assess trauma history using validated measures, including trauma duration and age at exposure. Another limitation of our study was missing post-treatment assessment of symptom severity, which was not limited to patients who dropped out of therapy. A primary reason for missing post-treatment assessment presumably was that there were no special requirements or incentives for therapists concerning post-treatment diagnostic assessment because of the naturalistic nature of the therapy setting. We applied Multiple Imputation (Rubin, 1987) to minimize bias due to missing data. Future studies conducted under routine care conditions should consider incentives for therapists to minimize missing data. Concerning the role of the therapist’s choice of interventions, we could not to investigate the reasons for the therapist’s decisions. The choice of intervention seemed to depend on the therapist’s personal style. Therefore, it remains open if a more targeted application of trauma-specific interventions could help trauma-exposed patients reach similar symptom levels as unexposed patients at the end of treatment. Future studies could, therefore, assess therapist’s reasons for applying certain trauma-specific interventions and assess the behavioral, emotional, and interpersonal problems for which each of these interventions is specialized. Furthermore, a more fine-grained assessment of symptom severity over time, combined with an assessment of the time interval in which a particular intervention was applied, would enable an in-depth analysis of the effects of intervention choice on symptom severity trajectories in naturalistic CBT.

Conclusion

In summary, our results highlight the frequency of childhood and adulthood trauma in the outpatient psychotherapy population, even without a PTSD diagnosis. Therapists should routinely screen for trauma history at the start of therapy using validated trauma questionnaires, as trauma history may influence therapeutically relevant characteristics like emotion regulation (Bridges-Curry & Newton, 2021) and interpersonal behavior (Shahab et al., 2021; Widom et al., 2018). We found overall symptom severity higher among trauma-exposed patients than non-exposed patients. Although patients with interpersonal and non-interpersonal trauma did improve throughout treatment in our study, the lack of differences in the relief of symptoms between patients with and without trauma suggests that other types of interventions might be necessary to ensure treatment success.
As not all trauma-exposed individuals suffer from long-term consequences (Glaesmer, Matern, Rief, Kuwert, & Braehler, 2015; Laugharne, Lillee, & Janca, 2010), assessing domains associated with trauma history and low therapy success in trauma-exposed patients at the start of treatment may be promising to identify those needing intensified treatment. These might be patients with subclinical PTSD symptoms, emotional dysregulation, interpersonal problems, or early-onset and recurrent symptoms. Therapists could then tailor interventions to the patient’s needs, offering, for example, skills training specifically to patients with (trauma-related) emotional dysregulation and Schema therapy or CBASP to patients with maladaptive attachment styles and interpersonal problems. For depressed patients with a trauma history, trauma-focused interventions like EMDR or Imagery Rescripting may also be effective (Dominguez, Matthijssen, & Lee, 2021). Modular psychotherapy (Elsaesser et al., 2022) could be a promising approach to individualized and evidence-based treatment.