Oxytocin administration during a
trauma analogue has been shown to increase intrusive memories, which are a core symptom of
post-traumatic stress disorder (
PTSD). However, it is unknown whether
oxytocin influences the acquisition or the consolidation of the
trauma. The current study investigates the effect of the activation of the
oxytocin system during the consolidation of an analogue
trauma on the formation of intrusive memories over four consecutive days and whether this effect is influenced by individual neurobiological, genetic, or psychological factors. We conducted a randomized double-blind placebo-controlled study in 217 healthy women. They received either a single dose of intranasal
oxytocin (24 IU) or placebo after exposure to a
trauma film paradigm, which reliably induces intrusive memories. We used a general random forest to examine a potential heterogeneous treatment effect of
oxytocin on the consolidation of intrusive memories. Furthermore, we used a poisson regression to examine whether
salivary alpha amylase activity (sAA) as a marker of noradrenergic activity and
cortisol response to the film,
polygenic risk score (PRS) for
psychiatric disorders, and psychological factors influence the number of intrusive memories. We found no significant effect of
oxytocin on the formation of intrusive memories (F(2, 543.16) = 0.75, p = 0.51, ηp2 = 0.00) and identified no heterogeneous treatment effect. We replicated previous associations of the PRS for
PTSD, sAA and the
cortisol response on intrusive memories. We further found a positive association between high trait anxiety and intrusive memories, and a negative association between the emotion regulation strategy reappraisal and intrusive memories. Data of the present study suggest that the consolidation of intrusive memories in women is modulated by genetic, neurobiological and psychological factors, but is not influenced by
oxytocin. Trial registration: NCT03875391.