Developing Intrusive Memories after Trauma: an experimental study on the effects of endocrine stress reactivity

To improve prevention of posttraumatic stress disorder, it is important to
increase our understanding of the biological and cognitive mechanisms
underlying the development of its hallmark symptom, i.e. intrusive memories.
Individual variation in endocrine stress reactivity to the traumatic event,
resulting in decreased contextual memory processing, is thought to underlie
intrusive memory development. Studying these process in more detail is only
feasible in healthy individuals using an experimental trauma paradigm. However,
the best currently available paradigm, the trauma film paradigm (consisting of
watching a film with aversive graphic footage of traumatic events) does not
result in consistent activation of the two most important stress systems, i.e.
the autonomic nervous system and hypothalamic-pituitary-adrenal axis, limiting
ecological validity of this paradigm and therefore hampering reliable
investigations into intrusive memory development. Therefore, the aim of this
study is to adapt this trauma film paradigm, which is expected to result in
more robust endocrine stress responses and increased frequency of intrusive
memories.

The primary objective is to investigate whether adding a brief mild
psychosocial stressor (socially-evaluated cold pressor test) immediately prior
to an experimental analogue traumatic event (trauma film paradigm) increases
acute endocrine stress reactivity (salivary cortisol and alpha amylase output)
throughout the experimental paradigm and increases intrusion frequency in the
following week. Secondary, it will be investigated whether addition of a
stressor affects voluntary memory accuracy and intrusion characteristics
related to the trauma film. Furthermore, the impact of individual variation in
endocrine stress reactivity throughout the paradigm and glucocorticoid receptor
functioning on voluntary and intrusive memories related to the trauma film will
be investigated.

Randomized controlled trial

Half of the participants will be randomized to the stressor condition, i.e. the
socially-evaluated cold pressor task, consisting of immersing their hand into
ice cold water while being videotaped for evaluation. The other half of the
participants will be randomized to the control condition, in which they immerse
their hand into lukewarm water without being videotaped. Thereafter, all
participants will watch a trauma film, known to induce intrusive memories in
the following week.

The study consists of three assessments, and include the experimental
procedures described above, questionnaires, cognitive tasks and non-invasive
assessment of biological stress reactivity. Additionally participants will
collect saliva for endocrine assessments at home for two consecutive mornings
and will fill out a short diary about intrusive memories for 7 consecutive
days. Study participants will not benefit from the research, and may experience
some short lived discomfort from the cold pressor task. Additionally, they will
likely experience some distress resulting from the trauma film and resulting
intrusive memories, which is however expected to have disappeared at one week
follow-up. The study is classified as moderate risk.