Nightmares: From terror to treatments

Dreams have long been a source of fascination for poets, psychoanalysts, and philosophers alike, all plundering the their contents for artistic inspiration or insight. Psychologists are no exception to the rule, with dreams being the focus of a number of psychological research studies.

Yet nightmares somehow escape the level of interest given to their more pleasant counterparts. According to the Oxford-based authors of a new study published in Clinical Psychology Review, nightmares are "rarely assessed in patients attending psychiatric services, and almost never directly treated" — despite their link with many mental health disorders. In their systematic review, the team explores whether manipulating nightmares causes changes in psychiatric symptoms, and whether their presence or severity predicts later mental health troubles.

To do this, the team searched a number of databases for papers published in peer-reviewed journals from 1980 to 2022, using a keyword filter of "nightmare" alongside key symptoms of psychiatric disorders including depression, anxiety, dissociation, schizophrenia, suicide ideation, bipolar, eating disorders, and personality disorders. To be included in analyses, papers had to contain quantitative measures of nightmares and psychiatric symptoms, an assessment of the relationship between the two, and a longitudinal or experimental design (with a significant between-group manipulation effect). 

The initial search resulted in 6,218 hits; after screening, 40 eligible papers remained, consisting of 24 longitudinal studies and 16 clinical trials. Several of these studies probed the relation of nightmares to suicidal ideation, depression, psychosis, and borderline personality disorder, while others looked at the path from nightmares to psychiatric symptoms in children and adolescents. 

Methodological shortcomings were common in the papers identified; in particular, many studies assessed nightmares with a single question. Even so, some interesting trends in the data did emerge.

The papers analysed by the team illustrated that not only are nightmares treatable, but that targeted treatment can also improve psychiatric symptoms. In the case of PTSD, studies with stronger methodology generally supported the idea that treating nightmares can lessen other PTSD symptoms. The review also found evidence that pre-trauma nightmares may be an early risk factor for later PTSD.

Several studies suggested that treating nightmares could lead to moderate improvements in depression, with two of these studies specifically finding improvements when using Imagery Rehearsal (a cognitive behavioural therapy technique designed to treat nightmares) and exposure therapy. Five trials showed that small to moderate improvements in anxiety could be made by addressing nightmares, with some research also suggesting Imagery Rehearsal may be effective. However, some of the studies looking at this were underpowered, and further research would be informative.

For psychosis, two cohort studies suggested risk of later psychosis was increased in those who had nightmares as children, even after adjusting for other potential factors. Some initial evidence also pointed to the potential for treating nightmares to ease paranoia. 

Evidence on the relationship between nightmares and personality disorders was lacking, with only one study investigating a causal relationship between the two. This study suggested that persistent nightmares in childhood were associated with later borderline personality disorder symptoms on adolescents. 

The review also revealed that nightmares predicted the later occurrence not only of suicidal ideation, but also attempts and completed suicide. For example, in an inpatient group who recently attempted suicide, frequent nightmares were associated with a three-times greater risk of a repeat suicide attempt over the next two years. However, two small pilot studies suggested that treating nightmares might prevent the recovery of suicidal ideation. No studies looked at whether suicidal ideation or attempted suicide caused nightmares.

Many of the studies included suggest that not only can treatment for distressing psychiatric symptoms reduce nightmares, but the inverse is also true — opening a potentially powerful avenue for healthcare workers and researchers looking to find interventions. 

However, it's important to note that these are not straightforward causal relationships. For instance, many of those being treated for PTSD may not see their nightmares reduced even if treatment is successful in reducing other symptoms. The team note that some patients may want to begin by treating nightmares, while others would benefit from general treatment that would potentially produce a reduction of nightmares anyway.

The authors also highlight the need for the development of robust measures of nightmares, as many of the identified studies found were lacking in this measurement. Methodological issues, such as power, lack of baseline measurement, and representative sample selection were also common. These limitations are common in under-researched areas, and in identifying both the limits and victories in the existing research on nightmares, the team effectively makes the case for more dedicated research in this topic.

Read the paper in full: https://doi.org/10.1016/j.cpr.2022.102241