Depression is among the world's leading causes of disability. To fill the existing treatment gap, psychological online interventions (POIs) and Internet-based treatment, including bibliotherapy with PDF manuals (POIs), are increasingly recommended as they are easily accessible and deemed an initial alternative approach. The present trial aims to evaluate imagery rescripting. With the help of various techniques, the approach aims to edit negative memories and rewrite a "happy end". To the best of our knowledge, imagery rescripting has never been tested as a self-help intervention. A large sample of patients with primary or secondary depression (N = 120) will be recruited and randomly allocated to either the intervention group or a wait-list control group. The intervention group consists of two subgroups that will receive either a full or brief version of a manual teaching them imagery rescripting. Participants will be assessed at baseline and six weeks later. A follow-up assessment will be completed six months later. The primary outcome measure is the Beck Depression Inventory II.

Depression is among the world's leading causes of disability. Effective pharmacological and psychotherapeutic treatments exist. However, only a subgroup of individuals with depressive symptoms receive proper treatment (Kohn, Saxena, Levav, & Saraceno, 2004). To fill the existing treatment gap (Kazdin, 2017), psychological online interventions (POIs) and Internet-based treatment, including bibliotherapy with PDF manuals (POIs), are increasingly recommended as they are easily accessible and deemed an initial alternative approach (i.e., "foot in the door") for persons who have reservations about face-to-face psychotherapy. E-mental health and bilbiotherapeutic interventions have yielded promising results, but there remains room for improvement as effect sizes are usually in the small to medium range. The present trial aims to evaluate imagery rescripting, a technique developed by Smucker (Smucker, Dancu, Foa, & Niederee, 1995). With the help of various techniques, the approach aims to edit negative memories and rewrite a "happy end". Positive mental imagery strategies seek to hold negative mental images in check and impart the patient with a feeling of self-efficacy. A new meta-analysis shows that imagery rescripting yields large effects on anxiety and depressive symptoms across a range of disorders (Morina, Lancee, & Arntz, 2017).

To the best of our knowledge, imagery rescripting has never been tested as a self-help intervention. A large sample of patients with primary or secondary depression (N = 120) will be recruited and randomly allocated to either the intervention group or a wait-list control group. The intervention group consists of two subgroups that will receive either a full or brief version of a manual teaching them imagery rescripting. Participants will be assessed at baseline and six weeks later. At post-assessment, the (full-length) manual will be made available to all participants. A follow-up assessment will be completed six months later. The primary outcome measure is the Beck Depression Inventory II. Secondary outcome measures include self-reported symptom measures (PHQ-9, GAF-7, Rosenberg Self-Esteem Scale, Global item from the WHOQOL-BREF). The project may help to answer the question of whether imagery rescripting is effective when presented using a self-help medium.

Inclusion Criteria:

• Electronic informed consent
• Internet access
• Adequate command of the German language
• Diagnosis of depression (primary or secondary)

Exclusion Criteria:

• Acute suicidality

self-report serves as outcomes, patients are not masked