Depression, characterized by low mood and diminished interest in previously rewarding activities, is a pervasive mood disorder and a global health concern (American Psychiatric Association, 2013; Ferrari et al., 2013; James et al., 2018; Whiteford et al., 2013). Despite the effectiveness of established psychological treatments like Cognitive Behavioural Therapy (CBT; Beck, 1970) in alleviating depressive symptoms, approximately 40% of patients do not respond adequately, underscoring the need for innovative interventions (Cuijpers et al., 2021; Zhdanava et al., 2021). The gap between the number of patients in treatment and treatment success points to the importance of further improving the treatment of depression.

A crucial aspect often overlooked in current psychological treatments is the presence of distressing memories, reported by about 80% of depressed patients (Brewin et al., 1996; Newby & Moulds, 2011a; Payne et al., 2019). These memories, even in the absence of traumatic events, predict depressive symptoms and persist to trouble patients who have recovered from depression (Buckman et al., 2018; Kuzminskaite et al., 2022; Nelson et al., 2017; Newby & Moulds, 2011b; Payne et al., 2019). Thus, distressing memories are not only common in depression but could also be a significant treatment target. Distressing memories are associated with unpleasant emotions such as sadness, shame, fear, or anger. While traditional CBT addresses cognitive and behavioural aspects of emotional problems, recent psychotherapy research underscores the importance of bringing the patient’s emotions into focus (Greenberg, 2010, 2017; Peluso & Freund, 2018). One technique to address both the distressing memories and the associated negative emotions is Imagery Rescripting (ImRs; Arntz & Weertman, 1999). ImRs, a therapeutic technique integrated into therapeutic approaches or used as a standalone intervention (Kip et al., 2023), addresses distressing memories in a two-step process (Arntz & Weertman, 1999). First, the individual vividly imagines the distressing memory, engaging various sensory modalities and experiencing the connected emotions. In the second step, the sequence of events is imaginatively transformed into a more desirable direction. This is achieved through the introduction of a supportive figure – such as the therapist or the patient’s adult self – who addresses the individual’s emotional needs. ImRs does not alter original memory content but aims to reduce the memory’s emotional meaning and emotional impact (Aleksic et al., 2024; Arntz, 2012; Arntz & Weertman, 1999). Arntz (2012) hypothesizes that the central mechanism of change in ImRs is the modification of maladaptive schemas, with emotional changes occurring as a by-product of this process. This perspective emphasizes the cognitive restructuring aspect of ImRs, where the reimagining of events leads to a shift in underlying belief systems, subsequently influencing emotional responses. Experimental research supports the idea that mental imagery has a profound impact on emotion (Holmes et al., 2008, 2009; Ji et al., 2016) and that ImRs reduces negative emotions and distress associated with negative memories (Çili & Stopa, 2021; Nilsson et al., 2012; Reimer & Moscovitch, 2015; Strohm et al., 2021). The positive impact of ImRs on negative emotions as well as on the distressing memories seems promising for the treatment of depression.

Despite its early recognition in CBT (Beck, 1970), the clinical applications of mental imagery within a CBT framework were relatively under-researched until recently, with pilot studies of ImRs as standalone interventions for depression demonstrating significant effects on symptom severity (Brewin et al., 2009; Ma & Lo, 2022; Pile et al., 2021; Renner & Holmes, 2018). Additionally, research has shown that engaging in mental imagery of future positive events can increase behavioural activation in individuals with major depressive disorder, further highlighting the potential of imagery-based interventions in depression treatment (Renner et al., 2017). Meta-analyses by Kip et al. (2023) and by Kroener et al. (2023) have further supported the efficacy of ImRs in treating various mental disorders associated with aversive memories, including depression, revealing large pre-post effect sizes across different disorders and highlighting its potential as a transdiagnostic intervention. Building on this evidence, a recent controlled pilot study by Kanczok et al. (2024) investigated the combined use of cognitive restructuring (CR) and ImRs compared to treatment as usual among inpatients with moderate and severe depression. The study found that patients in the intervention group (receiving CR and ImRs) achieved significantly greater improvements in depressive symptoms over time compared to the treatment-as-usual group. While these findings are promising, further research is needed to investigate the specific additional effect of using ImRs during regular cognitive behavioural therapy, particularly in outpatient settings and with larger sample sizes.

In addition to the open research questions regarding the extent to which ImRs affects depressive symptoms, there is also a lack of evidence regarding the potential mechanisms that play a role in ImRs. Studies have shown some evidence for different potential mechanisms on a cognitive level that might be responsible for the effect of ImRs: One aspect that several studies point out is the positive impact of ImRs on different aspects of a person’s self-representation (Lee & Kwon, 2013; Wild et al., 2008), self-belief (Cooper, 2011) and self-esteem (Çili et al., 2017). There are study results that indicate that the negative core beliefs associated with the distressing memories reduce in subjects treated with ImRs (Reimer & Moscovitch, 2015). Mancini and Mancini (2018) suggest that the effect of ImRs is based on a reduction of the ‘meta-emotional problem’, which is linked to a better acceptance of the negative emotions associated with the distressing memories. In the treatment of posttraumatic stress disorder (PTSD) related to traumas experienced in childhood, changes in strengths of encapsulated beliefs and distress of the index trauma preceded changes of PTSD-severity in ImRs (Rameckers et al., 2024), supporting the theory that change in emotional meaning of the memory underlies the effects of ImRs. Assmann et al. (2024) investigated the role of cognitions in the treatment of childhood-related PTSD using ImRs. Their study found that changes in trauma-related cognitions significantly mediated the relationship between ImRs and reductions in PTSD symptoms. These results highlight the critical role of cognitive processes in the effectiveness of ImRs and suggest that targeting maladaptive cognitions may be a key mechanism through which ImRs facilitates therapeutic change in PTSD. Further research is needed on the effects of ImRs on different aspects of cognition and emotion as well as on the ‘meta-emotional problem’.

Current research points to the problem that the effect of ImRs on depression has not been tested sufficiently in studies yet, especially not as an adjunct to regular cognitive behavioural therapy. Furthermore, the mechanisms of action of ImRs for depression remain unclear. This randomized controlled trial aims to expand the research on ImRs in depression. The primary objective is to evaluate the effectiveness of ImRs as an add-on to standard CBT for major depressive disorder (MDD). Patients receiving CBT in routine care are randomized to receive either three sessions of ImRs or an active control condition (imagery relaxation). We hypothesize that participants in the ImRs condition will show greater reductions in depressive symptoms from pre-intervention to post-intervention and follow-up. Although ImRs may be applicable across a range of disorders (Kip et al., 2023), we chose to focus specifically on depression in the present study for several reasons: First, the high prevalence of distressing memories among individuals with depression suggests a particularly strong clinical relevance of ImRs in this context (Brewin et al., 1996; Newby & Moulds, 2011a; Payne et al., 2019). Second, existing studies have primarily evaluated ImRs as a standalone intervention; its potential additive effect when embedded within standard CBT for depression remains largely unexplored. Third, depression continues to be among the most prevalent and burdensome mental health conditions, underlining the need for innovative adjunctive treatments. Given these considerations, we see depression as a particularly meaningful starting point for examining the clinical utility of ImRs. Importantly, comorbidities are not excluded in our study, reflecting the complex presentations often encountered in routine clinical practice. Secondary objectives of this trial include examining changes in associated psychological variables (e.g., repetitive negative thinking, emotional capabilities, self-compassion, self-esteem). In addition, exploratory analyses will investigate potential mechanisms underlying the effects of ImRs.

We presented a study protocol for a randomized controlled trial testing the additional effect of ImRs on depressive symptoms in individuals who are already in treatment (CBT). We hypothesized that, compared to an active control condition, the participants receiving ImRs would have a greater reduction of depressive symptoms.

While there are pilot studies showing significant effects of ImRs on depressive symptom severity (Brewin et al., 2009; Ma & Lo, 2022), this study aims to replicate and extend these promising results. Importantly, no studies have yet examined the additional effect of ImRs during regular CBT for depression. By investigating potential synergistic effects of ImRs and CBT, this study could provide valuable insights into enhancing treatment outcomes for depression. If participants in the ImRs condition show greater improvements in depressive symptoms, it would suggest a promising avenue for augmenting existing therapies. This is particularly significant given that current treatment options for depression are often insufficient for many patients (Cuijpers et al., 2021). Another important aspect that this study attempts to clarify is the underlying mechanisms that may be involved in the effect of the ImRs technique on depressive symptoms. This study contributes to the research on potential mechanisms by assessing the change of different psychological variables during the course of the study and by analysing exploratorily whether changes in psychological variables mediate the effect of ImRs on depressive symptoms.

One potential limitation of the study is that the therapists who conduct the experimental interventions of this study are not the same therapists who conduct the ongoing regular CBT. The ImRs and relaxation interventions are therefore not integrated into the ongoing treatment. Moreover, competence and experience levels of the therapists providing the ongoing regular CBT varies. While this approach enhances the ecological validity of our research, it introduces an analytical challenge. Because many therapists are involved in the regular therapy, and each therapist likely sees only few study participants, we can not effectively account for how individual therapists might influence the results. We do not have enough participants grouped with each therapist to reliably measure the impact that specific therapists might have on the outcomes. One other limitation is that the study is powered to find medium to large effects but is underpowered to find small or medium effects between the two active interventions. Furthermore, the effect size assumptions underlying the power calculation may be overestimated, as they are based on studies conducted without concurrent CBT, whereas in the present study, the intervention is delivered in parallel to ongoing psychotherapy. This parallel treatment setting may reduce the observable effect sizes and should be considered when interpreting the results. Finally, this study exclusively relies on self-report measures for primary and secondary outcomes. While this approach allows repeated, low-burden assessment, clinician-rated interviews could provide additional information on how many patients meet diagnostic criteria following the intervention. Additionally, we acknowledge that some participants might no longer fulfil the criteria for a Major Depressive Disorder diagnosis at the time of study inclusion, despite initially meeting them during screening. This should be considered when interpreting the results, as it may influence the generalizability and observed treatment effects.

Overall, we aim to expand the research on innovative interventions for depressive disorders with this study. The results will contribute to a better understanding of the effects of ImRs on depression, as well as its potential added value when delivered alongside ongoing cognitive behavioural therapy. Given that the primary outcome is assessed before the completion of CBT, interpretations regarding additive effects should be considered exploratory.