Abstract
The aim of this review is to evaluate the effectiveness of cognitive behavioral therapy (CBT) on nightmare frequency and to determine which kind of CBT is the most effective treatment. A systematic literature search was carried out in PsychInfo and PubMed articles published on or before May 1, 2008. The inclusion criteria were: nightmare treatment study, use of nonpharmacological treatment, not a qualitative case study, randomized-controlled trial (RCT). After selection, 12 peer-reviewed studies about 9 RCTs remained (2 follow-up studies and one displaying preliminary results). Several interventions have been reviewed including, recording one's nightmares, relaxation, exposure, and techniques of cognitive restructuring. The 12 evaluated articles varied in quality, and none fulfilled CONSORT guidelines. All articles used nightmare frequency as the primary dependent variable, and all found significant in-group differences (pre vs post) for intervention or placebo (range d = 0.7–2.9). Five studies were able to find a significant group effect for the intervention compared to a waiting list control group. Only one study found significant differences between 2 intervention groups. Nightmare-focused CBT (exposure and imagery rehearsal therapy [IRT]) revealed better treatment outcomes than indirect CBT (relaxation, recording). IRT and exposure showed no meaningful differences, but only one RCT directly compared both techniques. Three different research groups demonstrated the effects of exposure, but only one group showed the effect of IRT. Thus, RCTs that compare IRT with exposure by independent research groups are much needed.
Citation:
Lancee J; Spoormaker VI; Krakow B; van den Bout J. A systematic review of cognitive-behavioral treatment for nightmares: toward a well-established treatment. J Clin Sleep Med 2008;4(5):475–480.
Keywords: Nightmares, imagery rehearsal therapy (IRT), exposure, treatment, randomized controlled trial (RCT)
Nightmares are typically defined as extremely frightening dreams leading to awakening (Diagnostic and Statistical Manual of Mental Disorders, 4th ed. [DSM-IV-TR]),1 although definitions vary. For instance, the definition in the International Classification of Sleep Disorder, 2nd ed. (ICSD-2)2 does not limit negative emotions in nightmares to fear alone, as anger or sadness are also prevalent in nightmares.3 In the research literature, nightmares that do not lead to awakening are usually referred to as bad dreams,4 and nightmare induced distress5 is differentiated from nightmare frequency (NF): two related but independent constructs.
Studies of the general population have indicated that nightmares are highly prevalent, with up to 70% having occasional nightmares6 and approximately 2% to 5% of the adult population suffering from frequent nightmares.6–9 A similar percentage is estimated to “have a current problem with nightmares,” as frequent and chronic nightmares are associated with disrupted sleep,7 daily distress,4,8 and a variety of sleep complaints (e.g., night terrors,9 chronic insomnia,10 and sleep disordered breathing11,12) and affective complaints.13,14 Nightmares can have an idiopathic (unspecific) origin or occur as part of a posttraumatic stress disorder (PTSD).15 Approximately 50% to 70% of PTSD patients reports frequent nightmares.16
This high prevalence and impact of nightmares has resulted in several treatment outcome studies. In general, older studies on pharmacological treatment of nightmares (e.g., antidepressants) have shown poor results,17 while a recent systematic review on pharmacological treatment of posttraumatic nightmares showed that effects are inconclusive/tentative at best.18 The only clear exception is the α1-antagonist prazosin, which has shown very promising outcomes for posttraumatic nightmare reduction in 3 relatively small randomized controlled trials (RCTs),19,20,21 although it appears that prazosin must be used continuously as nightmares return after drug withdrawal. To date, cognitive-behavioral treatment (CBT) has gained more empirical support22 and is the treatment-of-choice for nightmares,14 particularly in long-term scenarios.
A range of cognitive-behavioral techniques seem to effectively decrease NF. Indirect CBT such as recording23 one's nightmares and relaxation exercises24 reduce NF. Nightmare-focused CBT such as exposure or systematic desensitisation24 and techniques of cognitive restructuring25 seem to decrease NF even more. These techniques mostly include recording and relaxation with an extra component. In exposure-related techniques, nightmares are written down and relived in imagination during the day. In cognitive restructuring techniques, nightmares are written down and thereafter changed in a (typically) more positive version. These changed nightmares can be relived during the day (imagery rehearsal therapy [IRT])26 or can be changed within the nightmare directly (lucid dreaming Treatment [LDT]).27 In a review, Wittmann et al.22 concluded that IRT has been evaluated most extensively but has been tested only by one research group.
To date different nightmare treatment studies have not been reviewed systematically. The aim of this review is to evaluate whether CBT shows effects on diminishing nightmare frequency as promising as those seen in RCTs, and if so, which kind of CBT is most effective.
METHOD
Search Strategy
A systematic literature search was carried out in PsychInfo and PubMed for articles published on or before May 1, 2008. The terms “nightmares” AND “treatment” were used. References from each relevant paper, including 3 recent reviews of the literature13.14.22 were examined for additional relevant studies.
The search strategy sought to obtain all relevant published databased RCTs based on the following criteria: nightmare treatment study, use of nonpharmacological treatment, not a qualitative case study, RCT. Follow-up studies were also included because they supplied information about the long-term effects of treatment. All RCTs on nightmare treatments for adults were reviewed by the first 2 authors.
Data Analysis
To adequately compare studies, Cohen's d was calculated for all studies with the software package G*power 3.0.5.28 Because all studies were paired-sample studies, the between-group correlations have to be taken into account when deriving Cohen's d. However, most studies did not supply the correlations between groups or sufficient data to calculate Cohen's d for a paired-sample study. To adequately compare the Cohen's d between studies, a conservative correlation between pre- and post-test measurement of r = 0.5 was used for all studies. No effect sizes could be calculated for one study29 because means and standard deviations were not reported, another study30 only supplied NF information (Both authors were contacted, but could not supply the missing data).
G*power 3.0528 was used to further explore the nonsignificant differences within- and between-groups. When there was no within-group (pre-post) (p > 0.05) effect over time, we calculated the sample size necessary to detect a significant effect (using the difference in effect size, assumption of dependent groups and a power of 0.8). If there was no significant effect in a study between 2 groups (e.g., intervention, waiting list), the sample size necessary to achieve adequate power (0.8) was determined (independent groups assumed).
RESULTS
Studies
The search string yielded 454 article titles in PsychInfo and 2645 in PubMed. After reviewing the abstracts, most articles were excluded because they were no-treatment articles. Of the remaining 108 articles, 70 were rejected because they were pharmacotherapy (30) or single case articles (40). The remaining articles were then reviewed; 17 of these were excluded because they were not controlled studies, one31 was excluded because it was in-group controlled, and one32 was excluded because the population was not >18 years of age. Twelve articles remained—9 studies,23–27,29,30,33,34 2 follow-up articles,35,36 and one article displaying preliminary results37 (see Table 1).
Table 1.
Search String
| PubMed | PsychInfo | |
|---|---|---|
| Treatment AND nightmares | 2645 | 454 |
| Treatment studies | 50 | 58 |
| Nonpharmacotherapy studies | 33 | 45 |
| No single-case studies | 17 | 21 |
| Controlled trials | 12 | 14 |
| Controlled-controlled trials | 11 | 13 |
| Population >18 years | 10 |
12 |
| Studies | 9 | |
| Follow-up articles | 2 | |
| Article displaying preliminary results | 1 | |
Study Characteristics
Of the articles we examined, 10 were written in the US, one in the UK,24 and one in the Netherlands27 (Table 2). The articles were published between 1978 and 2007. In the studies, a total of 437 participants were analyzed, the average number per study being 48.6 (SD = 35.8, range 20–114). In the 2 follow-up articles, intervention was offered to the waiting list (or recording condition) after 3 months.35,36 One preliminary37 and original26 study investigated sexual assault victims with PTSD and another study used students.30 The remaining studies recruited participants through advertisements in the general media.
Table 2A.
General Information Included Studies
| References | N* (m/f) | Treatment (start /completed**) | Type | Diary |
|---|---|---|---|---|
| Cellucci and Lawrence27 | 29 | Exposure (10/10) / Placebo (10/10) / Recording (9/8) | Ind | 8 weeks |
| Miller and DiPilato26 | 32 | Exposure (12/10) / Relaxation (12/11) / Waiting list (12/11) | Ind | 15 weeks |
| Kellner et al.32 | 26 (7/19) | IRT (14/13) / Desensitization (14/13) | Group / Ind | 1–2 month |
| Neidhardt et al.20 | 20 (4/15) | IRT (10/10) / Recording (10/10) | Group | 1 month |
| Krakow et al.37 | 19 (4/15) | IRT (10/9) / Recording (10/10) | Group | 1 month |
| Krakow et al.22 | 58 (13/45) | IRT (39/39) / Waiting list (19/19) | Group | none |
| Krakow et al.39 | 41 | IRT (53/41) | Group | none |
| Burgess et al.21 | 103 | Exposure (83/28) / Relaxation (61/33) / waiting list (62/42) | Self-help | 12 weeks |
| Krakow et al.30 | 91 (0/91) | IRT (87/43) / Waiting list (82/48) | Group | 3 weeks |
| Krakow et al.23 | 114 (0/114) | IRT (88/54)/ Waiting list (80/60) | Group | 3 weeks |
| Spoormaker and van den Bout24 | 23 (6/17) | LDT Ind (8/8) / LDT group (8/8) / Waiting list (7/7) | Group / Ind | none |
| Davis and Wright33 | 32 | ERRT (21/17) / Waiting list (22/15) | Group / Ind | 3 weeks |
ERRT = exposure, relaxation and rescripting therapy; IRT = imagery rehearsal therapy; LDT = lucid dreaming therapy
N = participants who completed treatment/first follow-up
Completed = treatment and first follow-up (with exception of follow-up studies)
Table 2B.
General Information Included Studies, Continued
| References | Measurements | Duration | Follow-up |
|---|---|---|---|
| Cellucci and Lawrence27 | NF / NI / NW / Anxiety | 5 weeks, 45–60 min a week | 1 / 2 weeks |
| Miller and DiPilato26 | NF / MMPI / POMS / DSS | 6 weeks, 45–75 min a week | After diary / 10 weeks |
| Kellner et al.32 | NF / NI / SQ / SCL-90 | One session | 4 / 7 / 10 months |
| Neidhardt et al.20 | NF / SQ / SCL-90 | One session | 3 months |
| Krakow et al.37 | NF / SQ / SCL-90 | One session | 30 months |
| Krakow et al.22 | NF / NW / SQ / VAS | One session | 3 months |
| Krakow et al.39 | NF / NW / SQ / VAS | One session | 18 months |
| Burgess et al.21 | NF / BDI / Fear | 4 weeks / hour a day | 1 month / 6 months |
| Krakow et al.30 | NF / NW / ND/ PSS / PSQI | 3 sessions (2 × 1 hour, 1 × 2 hour) | 3 month follow up |
| Krakow et al.23 | NF / NW / PSS / PSQI | 3 sessions (2 × 1 hour, 1 × 2 hour) | 3 months / 6 months |
| Spoormaker and van den Bout24 | NF / SRIP / SLEEP-50 | 1 × 2 hour session | 12 weeks |
| Davis and Wright33 | NF / NI / NW / BDI / PTSD / PSQI | 3 weeks, 2 h a week | 1week / 3 months / 6 months |
BDI = Beck Depression Inventory40; DSS = Dream Survey Schedule; Fear = Fear Questionnaire41; NF = nightmare frequency; NI = nightmare intensity; NW = Nights with nightmares per week; POMS = Profile of Mood States42; PSS = PTSD Symptom Scale43; PSQI = Pittsburgh Sleep Quality Index44; SCL-90 = Self-Report Symptom Inventory35; SLEEP-50 = sleep complaints45; SRIP = Self-Rating Inventory for PTSD46; SQ = symptom questionnaire36; VAS = Visual Analogue Scale (sleep).
The published trials we examined varied in quality, yet none fulfilled CONSORT guidelines.38 None of the articles explained how sample size was determined to achieve enough power. Only 3 articles26,29,34 explained how randomization was achieved, and one covered the issue of blinding the procedure.26
All articles described eligibility criteria of participants. For inclusion, most studies used a minimum NF of once a week. Miller and DiPilato29 used a minimum frequency of once a month. Cellucci and Lawrence,30 and Kellner et al.33 did not mention a minimum frequency. Other inclusion criteria were: 18 years or older,23,24,26,29,34,35,37 sexual assault survivors,26,37 posttraumatic stress symptoms,26,37 and having experienced a traumatic event.34 Exclusion criteria included alcohol/drug abuse,23,24,26,29,33–35,37 medication,23,25,27,29,35,36 psychosis/schizophrenia,25,26,33,34,36,37 severe (psychiatric) illness,24,29 and other sleep disorders.24,27
Three studies did not suffer from any dropout.23,26,27 Other studies mentioned the following reasons for dropout: failing to contact the participant, not sending back follow-up measurement, illness, got better. Krakow et al.26,37 and Davis and Wright34 found no statistical differences between completers and dropouts. Dropouts in the study of Burgess et al.24 were more often single and had fewer nightmares in the relaxation group at baseline. Moreover, this study suffered the highest dropout (42% for treatment condition); this attrition rate is, however, not abnormal for self help treatment.39
Four articles described an exposure type method,24,29,30,33 7 articles IRT,23,25,26,33,35–37 one study used “exposure, relaxation and rescripting therapy” (ERRT), an IRT-like technique,34 and one study used LDT.27 Most studies used a waiting-list control group, and one30 was placebo controlled. Four studies used a second intervention next to the control group. These second interventions consisted of relaxation,29 recording,23,30,35 and LDT group intervention.27 One study compared only 2 interventions without using a control group.33 Treatment duration from a therapist ranged from 450 minutes29 to zero minutes (self-help).24 Most studies used one to 3 treatment sessions.
All studies used a measurement for nightmare frequency; some studies used a diary to assess NF,24,30,37 others used interviews,29 the remaining studies used questionnaires.23,25–27,33,35,36 Some studies also measured nightmare intensity (NI),30,33,34 nightmare distress (ND)26,37 or amount of nights with nightmares per week.25,26,30,34,36 Most studies used questionnaires to assess other sleep complaints or mental health complaints.
To test for changes in time within- and between-groups, repeated-measures analysis of variance and subsequent paired t-tests, was used by most articles. Some used only paired t-tests,23,27 or did not describe their statistical analysis.29,30 One did not provide mean scores for variables,29 and one only reported mean scores for NF.30 Only 3 articles provided the intention-to-treat analysis.24,26,34
Intervention Efficacy
Key results for all the studies are displayed using standardized effect sizes (Cohen's d) in Table 3; for a quick overview, see Table 4. All articles used NF as a primary variable, and all found significant in-group differences (pre vs post) for intervention or placebo (range d = 0.7 to 2.9), and none for waiting list. Most studies found differences on secondary variables (range d = 0.4 to 1.6), one did not,27 and 3 found these differences for only one of their interventions.23,24,35 The insignificant findings might have been a result of a power issue as Spoormaker and van den Bout27 would have needed an intervention group of n = 22 to pick up the difference in effect found for PTSD. The same applies to Neidhardt et al,23 in which a sample size of 58 (SCL-90)40 or 61 (SQ)41 would have been needed per group to achieve adequate power to find this effect size. For the follow-up study,35 17 participants were needed to significantly find the difference of d = 0.7. Burgess et al.24 had enough power to determine effect sizes as small as d = 0.4.
Table 3.
Effect Sizes (Cohen's d) Included Studies
| NF | Nightmare intensity (distress) |
Nights week |
SCL-90 (BDI) |
SQ (fear) |
PTSD | SLEEP (PSQI) |
||
|---|---|---|---|---|---|---|---|---|
| Cellucci and Lawrence27 | Exposure / Placebo / Recording | 2.9/0.9/0* | n.a. | n.a. | n.a. | n.a. | n.a. | n.a. |
| Miller and DiPilato26 | Exposure / Relaxation / WL | n.a. | n.a. | n.a. | n.a. | n.a. | n.a. | n.a. |
| Kellner et al.32 | IRT / Exposure | 1.9/1.2 | 0.5/1.5 | n.a. | 1.3/0.8 | 1.6/0.8 | n.a. | n.a. |
| Neidhardt et al.20 | IRT / Recording | 1.3/0.7 | n.a. | n.a. | 1.1/0.3* | 1.4/0.3* | n.a. | n.a. |
| Krakow et al.37 | IRT / Recording | 0.9/0.7 | n.a. | n.a. | 1.1/0.3* | 1.2/0.7* | n.a. | n.a. |
| Krakow et al.22 | IRT / WL | 0.7/0.3* | n.a. | 1.3/0.1* | n.a. | 0.4/0.15* | n.a. | 0.8/+ 0.1* |
| Krakow et al.39 | IRT / WL | 1.6/n.a. | n.a. | 1.9/n.a. | n.a. | 0.5/n.a. | n.a. | 0.7/n.a. |
| Burgess et al.21 | Exposure / relaxation / WL | 1.1/0.3/0.1* | 0.2*/0.2*/0* | (0.8/0.1*/0.1*) | (0.6/0.1*/0*) | n.a. | n.a. | |
| Krakow et al.30 | IRT / Waiting list | 0.9/+ 0.3* | (0.6/0*) | 1.2/0.1* | n.a. | n.a. | 1.2/0.4* | 0.7/0.3* |
| Krakow et al.23 | IRT / Waiting list | 0.8/+ 0.1* | (1.1/0.1*) | 1.4/0.2* | n.a. | n.a. | 1.1/0.3* | 0.7/0.1* |
| Spoormaker and van den Bout24 | LDT ind / LDT group / WL | 1.4/0.3/0* | n.a. | n.a. | n.a. | n.a. | 0.6*/0.1*/+0.1* | 0.1*/0.2*/0.3* |
| Davis and Wright33 | ERRT / Waiting list | 0.8/0.3* | 1.7/0.3* | 1.0/0.2* | (0.6/+0.12*) | n.a. | 0.8/+ 0.1* | 1.2/0.4* |
ERRT = exposure, relaxation and rescripting therapy; IRT = imagery rehearsal therapy; LDT = lucid dreaming therapy; WL = waiting list * = no significant difference; n.a. = not available
Follow-up studies effect sizes displayed are compared to baseline
Table 4.
Quick Overview of Efficacy of (Groups of) Techniques
| Type of treatment | Technique | Effect size (Cohen's d) for NF reduction |
Effect on other sleep or affective complaints |
Amount of studies (n) |
Total participants (n) |
|---|---|---|---|---|---|
| None | Waiting-list | 0–0.3 ** | No | 4 | 154 |
| Indirect CBT | Recording | 0–0.7 * | No | 3 | 18 |
| Relaxation | 0.3 | No | 1 | 44 | |
| Nightmare-focused CBT | Exposure / Desensitization | 1.1–2.9 | Yes | 3 | 61 |
| Lucid Dreaming Treatment | 0.3–1.4 | No | 1 | 16 | |
| Imagery Rehearsal Therapy | 0.8–1.9 | Yes | 8 | 133 |
One study insignificant
All insignificant
Three IRT,25,26,34 and 2 exposure24,30 studies were able to find a significant group effect for the intervention compared to waiting list or placebo intervention. Burgess et al.24 also found significant differences between 2 groups (exposure and relaxation). Other studies were not able to display significant group-effects.23,27,33,35 This may be a power issue, because the sample sizes of these studies were small. Sample sizes of n = 52,33 n = 72,23 and n = 2427 were needed to detect significant (p < 0.05) differences in effect size with adequate power (0.8). Krakow et al.37 does not mention a significant group-effect in the preliminary study, but the final report does report these group-effects.26
DISCUSSION
Although the number of included studies is relatively small and the studied groups are quite heterogeneous, this first systematic review on nightmare treatment was able to demonstrate that nightmare-focused CBT showed superior effects to other forms of nightmare treatment for both nightmare reduction and amelioration of associated sleep and affective complaints. So while indirect CBT such as recording and relaxation are effective in reducing nightmares (but not associated complaints), nightmare-focused CBT demonstrated better results on all outcomes, most notably the techniques of exposure and IRT.
The only RCT comparing exposure with IRT found no statistical differences,33 and this systematic review could not conclude that one was more effective than the other. The only possible difference so far may be a trend that IRT seemed to reduce related affective complaints to a larger degree. It would be interesting to compare IRT to exposure in a sample with adequate power.
Although IRT has been studied in more RCTs than exposure (5 vs 3), all studies on IRT have been conducted by the same research group.22 According to APA criteria for empirically supported treatments42 this would mean that IRT is a probably efficacious treatment instead of a well-established treatment (criterion V for well-established treatments: effects must have been demonstrated by at least 2 different investigators or investigatory teams). Criterion I, “superior to pill or psychological placebo or to another treatment,” has not been fulfilled yet for IRT, as the only nightmare study so far with statistically significant differences between interventions was that of Burgess et al,24 which showed stronger effects for exposure than for relaxation. Moreover, the effects of exposure have been demonstrated by 3 different research groups, making it the only well-established treatment for nightmares so far.
Including the ERRT as employed by Davis and Wright34 as an IRT-like technique, may help lift the status of IRT, but RCTs following CONSORT guidelines38 evaluating IRT by independent research groups are much needed. Comparisons should be made with other techniques (well-established ones such as exposure and/or psychological placebo like recording), and pharmacological treatment (e.g., prazosin) in larger samples with sufficient power; assessment should focus on nightmare (frequency and distress), sleep, and affective (anxiety, PTSD, and depressive) complaints.
DISCLOSURE STATEMENT
This was not an industry supported study. Dr. Krakow owns and operates Maimonides Sleep Arts and Sciences, Ltd., a for-profit sleep medical center and has published the following intellectual properties: Books – Insomnia Cures, Turning Nightmares Into Dreams, and Sound Sleep, Sound Mind; Websites – www.sleaptreatment.com, www.nightmaretreatment.com, and www.sleepdynamictherapy.com. The other authors have indicated no financial conflicts of interest.
ACKNOWLEDGMENTS
This study has been made possible due to financial aid of the Netherlands Foundation for Mental Health, located in Utrecht, the Netherlands. We would like to thank Eveline van den Heuvel for her valuable comments.
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