Trauma‐related rumination mediates the effect of naturally occurring depressive symptoms but not momentary low mood on trauma intrusions

Comorbid depression is known to contribute to the maintenance of posttraumatic stress disorder (PTSD) including distressing intrusive trauma memories. It is theorised that depression is a risk factor for persistent PTSD through preventing optimal habituation of distress provoked by trauma memories and reminders, but the underlying cognitive mechanisms responsible are uncertain. The present study investigated trauma‐related rumination as a possible mediator for the effect of depression on trauma intrusions. Participants received a low mood induction or control procedure. Following viewing an analogue trauma film, frequency of film‐related intrusions and associated distress levels were measured and at 1‐week follow‐up. Between the two occasions, participants rated their levels of rumination about the film. Existing depression symptoms but not induced momentary sad mood predicted frequency of film intrusions and associated distress at 1‐week follow‐up. Some evidence was found that ruminative trauma processing mediated the relationship between baseline depressive symptoms and later intrusion frequency and associated distress. Future research is warranted to better understand the role of rumination in the depression–intrusion relationship, which may shed light on the clinical applicability of rumination‐targeted intervention for PTSD and comorbid depression.