Understanding posttraumatic nightmares

A common symptom of posttraumatic stress is having nightmares, where a person re-experiences their traumatic experience in some way while they sleep.

But, what we are starting to suspect is that not all posttraumatic stress disorder (PTSD) nightmares are the same, and that has important implications for how we go about treating them.

One promising and relatively simple psychological intervention for PTSD nightmares has been to have patients consciously ‘rescript’ their nightmare in a way that increases their sense of mastery or control, and steers the storyline in a different direction before it reaches the most distressing part.

We call it imagery rehearsal therapy.

But, after encouraging initial studies on the effectiveness of imagery rehearsal in PTSD, larger and more rigorous studies are yielding more unclear treatment outcomes.

So why would it work for some people and not others?

Recent polysomnography (sleep monitoring) research into posttraumatic nightmares is suggesting that these dreams differ from normal ones in several ways and may actually be a range of phenomena, rather than a single one.

Imagery rehearsal therapy was first introduced by British psychiatrist Isaac Marks 40 years ago, originally as an intervention to help children to overcome repetitive bad dreams.

Since then, research into the use of imagery rehearsal in the treatment of posttraumatic nightmares in adults with PTSD has grown.

The early pilot studies conducted by researchers around the world, including us at Phoenix Australia, showed very promising results.

So much so, that imagery rehearsal was named as a Grade A recommended treatment for nightmares, including in PTSD, in the American Academy of Sleep Medicine (AASM) Best Practice Guide for the Treatment of Nightmare Disorder in Adults.

However, the results of recent randomised controlled trials have been more equivocal. For instance, I was involved in a recent study of US Iraq and Afghanistan veterans that compared imagery rehearsal in combination with cognitive behavioural therapy for insomnia (CBT-i) to CBT-i alone.

Both the frequency of nightmares and the distress they caused were reduced in both groups, but there was no significant difference in results between the groups.

Almost a third of all participants experienced a clinically significant reduction in nightmares and in 22 per cent the nightmare stopped.

So, it appears that imagery rehearsal therapy is effective for some but not for all sufferers of posttraumatic nightmares.

The critical next step in research is to address the question of who is likely to benefit from imagery rehearsal therapy and who is not. Or perhaps more specifically, in what type of posttraumatic nightmares can imagery rehearsal be effective?

In our previous research, we and along with other researchers including those in The Netherlands and the US, have investigated people’s self-reported experience of posttraumatic nightmares.

Research finds that these nightmares vary in the extent to which they are more like normal dreams, where the content can appear simply bizarre, or more like PTSD intrusions, where the nightmare replicates actual traumatic events.

More recently, in collaboration with Austin Health, we have been investigating the experience of posttraumatic nightmares using portable polysomnography.

In the past, researchers have had limited success in investigating posttraumatic nightmares in sleep studies because they simply tend not to occur in sleep laboratories.

In our study, we asked participants to press an ‘event button’ when they awoke from a nightmare. This was linked with their sleep record, which then allowed us to determine in what stage of sleep the nightmare arose, and the timing of waking in relation to changes in heart rate or other sleep events.

One of the key findings of this study was that, unlike normal dreams, posttraumatic nightmares occur during both rapid eye movement (REM) sleep, which is when we tend to dream, as well as non-REM sleep.

We also found that the posttraumatic nightmares generally occurred alongside other sleep disturbances, most commonly respiratory problems associated with obstructive sleep apnoea and/or unconscious leg movements.

And, unlike normal anxiety dreams in which there is a gradual increase in anxiety that eventually leads to awakening, participants in our study experienced a rapid increase in heart rate at the time of awakening.

The association between posttraumatic nightmares and this range of factors adds weight to the suggestion that the posttraumatic nightmares of PTSD may not be a single phenomenon but, instead, a range of different phenomena, influenced by normal dreaming, the nature of PTSD intrusions and sleep related processes.

So where does this leave us?

To date, studies of imagery rehearsal therapy have found the intervention to be effective for some but not for all posttraumatic nightmares.

If posttraumatic nightmares incorporate a range of phenomena – some like normal REM dreams, some triggered by sleep events and others manifesting as PTSD intrusions – it’s likely that treatment needs to be tailored differently to each.

Future research now needs to investigate what type of intervention is best for what type of posttraumatic nightmare.

But, in the meantime, it means that a variety of treatments need to be considered for posttraumatic nightmares – whether it is treatments aimed at underlying sleep disorders, like pressure ventilators in the case of sleep apnoea, CBT-i to improve sleep, as well as imagery rehearsal.

So, clinicians need to be familiar with all treatments and prepared to use a combination or sequence of them to determine what works best for each individual client.

A good night’s sleep is a matter of finding the right type of treatment for the right type of nightmare.

Associate Professor Phelps will be presenting a clinical tutorial on imagery rehearsal at the Australasian Conference on Traumatic Stress (ACOTS) in Sydney, 13-14 September, 2019.

ACOTS is a collaboration between Phoenix Australia and the Australasian Society for Traumatic Stress Studies. The conference’s keynote speakers are Professor Richard Tedeschi, Professor Emeritus at the Department of Psychological Science, University of North Carolina, Professor Frank Neuner, head of Clinical Psychology at Bielefeld University, Professor Richard Bryant, Scientia Professor and Director of the Traumatic Stress Clinic at the University of New South Wales, and Professor Kim Felmingham, Chair of Clinical Psychology at the University of Melbourne.

Banner: Close up of a polysomnography/Getty Images