Chapter 53 Dreams and Nightmares in Posttraumatic Stress Disorder

Abstract

Posttraumatic stress disorder (PTSD) develops in a significant minority of persons who are exposed to severely threatening trauma. Trauma-related nightmares appear to be specific to PTSD and can be a persisting and distressing symptom. Not all dream content reported by persons with PTSD is a direct representation of trauma memories, however. Stress and trauma appear to acutely affect the thematic content of dreams irrespective of whether the dreamer goes on to experience continuing emotional distress. Dreams that more specifically replicate the memory of the trauma during the early aftermath of exposure have been associated with the development of PTSD. In addition to indicating that stressful experiences are incorporated into dream content, findings from experimental and naturalistic studies further suggest that dreams can positively influence adaptation to stress and trauma. Persisting trauma-related nightmares might represent a failure of adaptive mechanisms.

Findings from polysomnographic studies of PTSD have not been entirely consistent. More-recent studies suggest that the majority of nightmare episodes of study subjects with PTSD arise from REM sleep, although they can also be accompanied by NREM sleep. A more-fragmented pattern of REM sleep during the month following trauma is associated with the development of PTSD.

In contrast to normal dreams, dreams in persons with PTSD often incorporate actual memories of frightening experiences. These features have implications for understanding dreams’ neurocognitive substrates. There is evidence that pharmacologic antagonism of noradrenergic receptors ameliorates nightmares in PTSD. Treatments that use cognitive restructuring of nightmare content have also yielded promising results.

Replicative-Trauma Nightmares: Hallmark of a Disorder?

Posttraumatic stress disorder (PTSD) is a psychiatric condition that develops in some but not all persons who experience severely threatening traumatic experiences (see also Chapter 129). The diagnosis is based on persisting symptoms that include re-experiencing the trauma with intrusive images, flashbacks, or nightmares; emotional numbing and avoidance behavior; and heightened arousal. The course of PTSD can be self-limited, but in approximately a third of cases it persists for many years, and it often manifests with comorbid psychiatric disorders.¹ The fourth edition of the Diagnostic and Statistical Manual (DSM-IV-TR) specifically delineates “recurrent distressing dreams of the event” among re-experiencing symptoms.² In an influential review and theoretical paper, Ross and colleagues emphasized the occurrence of “repetitive replicas” of trauma scenes as a feature of dreams that is virtually specific to PTSD, further referring to trauma nightmares as a “hallmark of the disorder.”³

Treating patients who have PTSD often leaves the clinician impressed with the impact of distressing dreams featuring traumatic experiences. Several studies support the specificity of the relationship between trauma-related nightmares and PTSD proposed by Ross’s group.³ Van der Kolk and colleagues⁴ reported that patients with combat-related PTSD were more likely to indicate that their nightmares exactly or almost exactly replicated an actual event, as compared with nightmare sufferers who did not have PTSD. Mellman and coworkers⁵ surveyed combat veterans from clinical and nonclinical settings and found that nightmares about combat experiences were more specifically associated with PTSD than were nightmares on other topics. In an analysis of a large epidemiologic database from Vietnam veterans, a measure that combined instances of nightmares related to military experiences and of distress from dreaming was strongly associated with PTSD.⁶

Thus there is consistent support for the theory that continuing representation of trauma memories in dreams is a feature of PTSD but not necessarily of trauma exposure absent the diagnosis. The aforementioned studies relied on retrospective and global, categorical assessments of dreams. Esposito and coworkers ⁷ performed content analysis of dreams elicited from morning diaries in a group of combat veterans receiving treatment for PTSD. About half of subjects’ dreams contained direct references to combat experiences, and almost all of the dreams featured threat. The majority of dreams were also not unlike normal dream reports in containing implausible elements that were not representations of actual memories. Kramer and colleagues⁸ also found in a symptomatic combat veteran group that about half of the dreams elicited after awakenings in the laboratory setting referred to military experiences. These studies all focused on combat veterans many years after their combat experiences.

Several studies have examined the influence of trauma on dream content during an acute phase following the traumatic event. In the 2 months following Hurricane Iniki, which struck Hawaii in 1992, dream questionnaires from 22 primary care patients were compared to a larger sample surveyed prior to the hurricane (N = 265). A significantly higher percentage of the posthurricane subjects reported that their dreams were related to general stressors (74% versus 48%) and to “especially stressful life experiences” (67% versus 37%), although only 13% reported dreams specific to the hurricane.⁹ Similarly, evacuees of the East Bay fire (Oakland and Berkeley, California, in 1991) were more likely to have recorded dreams in their home diaries with content related to death, disasters, and fires than were controls.¹⁰ Incorporation of trauma content in the dreams of recently traumatized children was reported by all 23 children kidnapped and buried underground in a trailer,¹¹ in 8 of 10 who witnessed rapes,¹² and in 63% of those on a playground during a sniper attack.¹³ Unfortunately, these studies did not relate dream content to PTSD or acute stress disorder status, although the study of the sniper attack did document higher rates of trauma dreams as a function of proximity to the threat.

Mellman’s group ¹⁴ elicited dream content from study participants during the acute aftermath of traumatic injury. A subgroup of the sample described dreams that were distressing and “highly similar” to the traumatic experience (17% of the sample; 56% of those who reported dreams). This group had more severe concurrent PTSD symptom ratings than the groups with other categories of dreams, and they had higher subsequent PTSD severity than the group that did not recall dream content.¹⁴

Thus, exposed populations tend to report dreams with specific trauma-related or thematically related content during the acute aftermath of disasters and other traumas, and dreams that are similar to the memory of the actual traumatic event are associated with the development of PTSD. Chronic PTSD is associated with recurring dreams that represent specific memories of a traumatic experience. However, the more comprehensive evaluations of dreams during chronic phases of PTSD document that salient dream content is not limited to representations of traumatic memories.

Dream Content With Stress and Trauma: Beyond Replication

Although the issue of trauma replication has received the most attention, there are descriptions of other aspects of content in the literature on dreaming, nightmares, and PTSD. The boundaries of traumatic stress are not always clear, and the topic seems embedded in broader questions of stress and dreaming, including observations of the impact of stressful experiences on dreams, the influence of dreams on adaptation to stressful experiences, and content themes related to trauma exposure and PTSD beyond replication of trauma.

Stress and Dream Content

A number of studies of naturalistic stressors have suggested an impact of stressful waking experiences on dream content. For example, health-related stressors have been evidenced in the home dream content of patients awaiting surgery ¹⁵ and in hospitalized burn patients.¹⁶ Dreams in pregnancy have been interpreted as reflecting concerns about the body and about the ability to mother and nurture.¹⁷ In addition, the dreams of women with stressful menstruation are more likely to contain emotional content and relationship themes during the peak hormonal phase compared with other days in the menstrual cycle.¹⁸

Academic and occupational stress might also influence dream content. Duke and Davidson ¹⁹ found increased dream recall in a week before exams compared with a control week in college students. In contrast, Delorme, Lortie-Lussier, and De Koninck²⁰ found no difference in dream content involving exams or negative emotions 10 days before and after exam periods, although the authors failed to find a difference in the students’ reported stress levels between the two periods. During one of the worst weekly performances of the Dow Jones Industrial Average, significant correlations were found between stockbrokers’ stress levels and negative dream features, including recurrent nightmares, dreams of being chased, and dreams of falling.²¹

It has been noted that recurring dreams, which have more negative content than nonrecurring dreams,²² tend to be activated by stressful life experiences.²³^,²⁴ In a community sample, subjects with active recurring dreams reported greater life stress in the prior 6 months and had more negative dream content than both former recurrent dreamers and dreamers who had never had recurrent dreams.²³ These findings were replicated in two college student samples.²⁵^,¹⁹

In addition to these naturalistic observations, studies have used experimental induction of stress and examined dream content. Disturbing movies,²⁶^,²⁷ sham intelligence exams,²⁸^,²⁹ deprivation of liquids,³⁰ and experimentally induced pain³¹ have all been incorporated into dreams collected in the sleep laboratory. Overall, experimental stressors are associated with subsequent dreams that are characterized by a negative tone.

This almost uniform support for incorporation of stressful experiences into dream content contrasts somewhat with the debate and mixed findings around the broader question of whether dreams tend to incorporate recent experiences and waking concerns.³²^–³⁶ Although there is evidence that relatively innocuous daytime events and concerns can be incorporated into dreams, it seems reasonable to infer from the studies we have reviewed that stressful waking experiences are more likely to be incorporated into dreams and have an impact on dream emotional content. This relationship of dream incorporation to emotional saliency has led researchers to invoke an emotional information processing function for dreaming.^22,³⁷^–⁴⁰ Although this contention is difficult to confirm, several lines of evidence support a relationship between dreams and adaptations to emotional stress.

Dreams and Adaptation to Stress

Two experimental studies suggest that dream content is related to adaptation to stress. In the study of liquid deprivation, subjects who had their thirst quenched in their dreams were less thirsty in the morning than those who had liquid in their dreams and remained unquenched or who had unrelated dreams.³⁰ In one of the experiments that used viewing a disturbing film as a probe, subjects experimentally deprived of REM sleep were subsequently more distressed by the film than either a NREM-sleep interruption group or an uninterrupted sleep group.²⁶

Naturalistic studies suggesting that dream incorporation can aid adaptive processing include several that found that references to drugs and alcohol in dreams are a positive predictor of abstinence,⁴¹^–⁴⁴ including smoking cessation.⁴⁵ Cartwright and colleagues³⁸ elicited dream reports following laboratory awakenings from REM sleep in men and women going through divorce near the time of the initial breakup and one year later. Those who incorporated the ex-spouse into their dreams at the time of the breakup were less depressed and better adjusted at 12-month follow-up than those who did not. These two sets of observations might initially seem to contradict the observations reviewed earlier of an association between trauma-replicating dreams and the outcome of PTSD. The observations just reviewed, however, refer to incorporation of a reference or representation of a stressful situation and not necessarily the replication of events.

For dreaming to influence emotional adaptation to stress, the neurocognitive activity of sleep must have an enduring influence on memory representations. Although the theory remains controversial, there is increasing support for a role for sleep in the consolidation and reprocessing of memory (i.e., learning) that is reviewed in preceding chapters of this text.

Trauma, PTSD, and Content Themes

Dow and colleagues ⁴⁶ studied depressed combat veterans with and without PTSD. They examined dreams collected from both groups in the sleep laboratory after awakenings from REM sleep. The PTSD group’s dreams were rated higher for anxiety and were more likely to have been set in the past. Another laboratory study of veterans found more frequent aggression in the dreams of subjects with combat-related PTSD compared to the dreams of healthy controls.⁴⁷ Ratings for anxiety, aggression, and interpersonal conflicts were greater in the dreams of a symptomatic subgroup of Holocaust survivors.⁴⁸ In a study of combat-related PTSD where dream recall was stimulated using diary records filled out in the morning, threatening content was observed in the majority of dreams (83%) with and without the presence of combat references.⁷ In contrast, although the dreams from five female college students with PTSD were found to be more vivid and descriptive than dreams from five matched controls, they were not more negative, repetitive, or oriented to the past.⁴⁹

Studies relating dreams to trauma exposure in children have also described content themes beyond representation of the trauma. The dreams of Palestinian children exposed to ongoing civil and military violence, elicited by home diaries, contained more themes of aggression, persecution, and negative emotions than dreams recorded by children living in a more peaceful region.⁵⁰ Kurdish children with trauma exposure evidenced more dreams with threat and aggression than either a nonexposed group or a control group from a peaceful country.⁵¹ Unfortunately, neither of these studies determined the PTSD status of their subjects.

In our own study of patients with recent traumatic injuries, dreams contained less friendliness and sexuality compared with dreams from a normative sample of dreamers.⁵² The dreams of those who developed PTSD had more content related to general and physical misfortune, as well as more negative emotions, than those who did not develop PTSD. Thus, compared to other dreams, dreams after trauma have more general negative emotions, anxiety, threat, and aggression, and these appear to be most pronounced with PTSD.

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