Rationale: Patients with post-traumatic stress disorder (PTSD) experience highly frequent
and distressing intrusive images depicting earlier aversive experiences. Not only
patients with PTSD experience these intrusions; they are also very common in depression.
Therefore, trauma treatments that target these intrusions may also benefit patients with
depression. Additionally, comorbid depression in patients with PTSD reduces the effects
of trauma treatment. It is currently unknown which treatment for traumatic intrusions is
most effective for patients who meet criteria for PTSD, depression, or both, and
treatment selection is often a process of trial and error. The mechanisms of action of
trauma treatments may inform us how to select the most appropriate treatment for a
particular individual.
Objective:
The investigators' primary objective is to investigate which treatment (EMDR vs. IR) is
most effective for different groups of patients who experience intrusions: patients with
PTSD, patients with depression, or patients with PTSD and a comorbid depression. To this
end, the investigators will examine the reduction in the severity of intrusions (i.e.,
frequency, uncontrollability, and degree of interference with daily life). The
investigators' secondary objective is to gain more insight into the mechanisms of action
of EMDR and IR. To this end, the investigators will examine the role of various mediators
of the treatment effects (i.e., the reduction in the severity of intrusions). The
investigators will specifically investigate the potential mediating roles of
self-compassion, emotion regulation, positive affect, rumination, and the vividness,
distress, and associated meaning of intrusions.
Study design: This study will use a single-case experimental design (SCED). In this
design, a small group of patients is followed throughout their treatment. It is a
within-subjects design in which each patient undergoes a baseline phase (2 weeks prior to
the start of treatment) in which no intervention takes place, an experimental phase with
treatment interventions (at least 2.5 weeks), and finally a withdrawal phase (4 weeks
following the last intervention session) in which no further treatment takes place.
Study population: This study will recruit 42 patients meeting criteria for either PTSD or
depression, or for both disorders.
Intervention (if applicable): Patients will be randomly assigned to standard treatments
EMDR or IR. In each condition, patients will receive two 75-minute sessions of EMDR or IR
each week, as well as an additional coaching session each week. Treatment length depends
on patients' needs and varies between 2.5 and 6 weeks.
Main study parameters/endpoints: The primary outcome is a brief measure of
characteristics of intrusions (specifically, the frequency, uncontrollability, and degree
of interference with daily life), which will be assessed twice daily via an online mobile
app.
Additionally, process measures indexing possible mediators concern brief questionnaires
on emotion regulation, self-compassion, rumination, positive affect, and the vividness,
distress, and related meaning of intrusions, which also serve as the investigators'
primary outcome measures. These questionnaires will be assessed daily. All primary
outcome measures will be administered during the baseline, experimental, and withdrawal
phase. Secondary outcome measures concern questionnaires on quality of life, depression
symptoms, and PTSD symptoms which are endorsed at the pre-intervention assessment (i.e.,
2 weeks prior to the first intervention session), post-treatment assessment (i.e., 4
weeks after the last intervention session, at the end of the withdrawal phase), and at
6-month follow-up assessment.
