Lecture 13 2025 - Nightmares

Nightmares: Medical Definition

• Nightmares are defined medically as extended, extremely dysphoric dreams usually involving efforts to avoid threats to survival, security, or physical integrity.
• The earlier medical definition included a criterion that the nightmare would awaken the dreamer.
• Nightmares are different from night terrors, which are disorders of arousal where dreams aren't recalled.
• The average incidence is 1-2 per year, but 10-25% of people experience one or more nightmares per month.

Idiopathic vs. Post-Traumatic Nightmares

• It's important to distinguish between idiopathic nightmares (spontaneous or of unknown cause) and post-traumatic nightmares.
• PTSD nightmares are more likely to be repetitive and occur earlier in the night.

Differences in Nightmare Characteristics: PTSD vs. Lifelong Nightmare Groups (Hartmann, 1996)

• Study comparing veterans with PTSD nightmares to those with lifelong nightmares (LL).

• PTSD group: Frequent nightmares started during or after combat experience, diagnosed with PTSD.
• LL group: Lifelong history of nightmares, no combat experience.

Psychoticism and Neuroticism

• Some studies have found differences in psychoticism and neuroticism between frequent and non-frequent nightmare sufferers.

MMPI Findings in Subjects with Nightmares and Normal Control Subjects (Kales et al., 1980)

• Significant difference between groups by Student's t-test (p<.01).

Characteristics of the Frequent Nightmare Sufferer (Berquier & Ashton, 1992)

• Compared 30 lifelong nightmare sufferers to 30 controls.
• Dreams recorded for one month.
  • NM group: 23.3 dreams, 5.9 rated as very frightening.
  • Control group: 10.9 dreams, none rated very frightening.
• Nightmare sufferers scored significantly higher on EPQ-N (Eysenck Personality Questionnaire - Neuroticism) and other psychopathology measures.

Nightmare Sufferers: Means, Standard Deviations, Univariate F Ratios, and Standardized Discriminant Function Coefficients for Both Groups (Berquier & Ashton, 1992)

• EPQ= Eysenck Personality Questionnaire; all other scales are from the Minnesota Multiphasic Personality Inventory.
• *p < .01. p<.001.
• **

Disturbing Dreams and Anxiety (Nielsen et al., 2000)

• Adolescents with frequent disturbing dreams scored higher on anxiety both at the time of the study and 3 years later.
• Significant differences in anxiety scores based on recall frequency of disturbing dreams at ages 13 and 16.

Thin-Boundariness and Nightmares

• Possible association with Hartmann's thin-boundariness.

Dream Content Variables (Hartmann et al., 1991, Dreaming)

Influence of Acute Stress on Frequency of Nightmares

• Wood et al. (1992) investigated the effects of the 1989 San Francisco earthquake on the frequency and content of nightmares.
• Nightmare frequency was about twice as high among students in the San Francisco Bay area compared to control participants in Tucson, Arizona, after the earthquake.
• California participants had more nightmares in general and substantially more about earthquakes.
• 40% in the San Francisco Bay area reported one or more nightmares about an earthquake, compared to only 5% in Arizona.
• However, nightmares about earthquakes were not more emotionally intense than other nightmares.

Measurement of Nightmare Frequency

• Retrospective estimates of nightmare frequency tend to be under-reported.
• Nightly log estimates are far higher than retrospective estimates.
• Wood and Bootzin (1990) found that using daily dream logs (2 weeks) with undergraduates:
  • 47% had at least one nightmare.
  • Equivalent annual frequency was 23.6, 2.5 times higher than retrospective methods.
  • Uncorrelated with self-reported anxiety.

Nightmare Prevalence in the Elderly (Salvio et al., 1992)

• Elderly participants had 65% of the number of nightmares of college students.
• They were 1/5th as likely to report having a problem with nightmares.
• Nightly log estimates were 10 times higher than retrospective estimates.

Comparison of Elderly and College Students: Demographic Data and Reported Nightmare Characteristics (Salvio et al., 1992)

Nightmare Distress (Belicki, 1992)

• Measured trait nightmare distress with a questionnaire (see original document for full questions). Some of the questions included:
  • When you awaken from a nightmare, do you find you keep thinking about it and have difficulty putting it out of your mind?
  • Do you ever find yourself avoiding or disliking or fearing someone because they were in your nightmare?
  • Are you ever afraid to fall asleep for fear of having a nightmare?
  • After you awaken from a nightmare, do you have difficulty falling back to sleep?
  • Do nightmares interfere with the quality of your sleep?
  • Do you have difficulties coping with nightmares?
  • Do you feel you have a problem with nightmares?
  • Do nightmares affect your well being?

Nightmare Frequency and Distress (Belicki, 1992)

• Moderate relationship between nightmare frequency and nightmare distress.

Correlations with Nightmare Variables (Belicki, 1992, J Abnormal Psych)

• Waking life negative wellbeing is more related to nightmare distress (reaction to nightmares) than to retrospectively assessed frequency of nightmares.

• *p<.05. ** p<.01.

Nightmare Distress as a Confound

• Nightmare distress is a confound for studies assessing the relationship between waking life well-being and nightmare frequency.
• This is due to the possibility that negative well-being causes ND, leading to high NF reports, or participants with high NF self-selecting into studies.
• It's necessary to correlate waking life well-being variables with nightmare frequency (assessed by logs) and nightmare distress in one study.
• Blagrove et al (2004). Journal of Sleep Research.

Psychopathology Variables (Blagrove et al, 2004)

• POMS Elated - Depressed
• POMS Composed - Anxious
• EPQ Neuroticism
• General Health Questionnaire - Stress and physical symptoms

Dream Variables (Blagrove et al, 2004)

• Retrospective nightmare frequency
• Belicki's trait nightmare suffering
• 2-week log nightmare frequency
• 2 – week log nightmare and dream tone
• 2 – week unpleasant dream frequency
• Nightmare defined as a very unpleasant dream that wakes up the dreamer
• Unpleasant dream frequency defined as a very unpleasant dream irrespective of whether or not the dream woke the dreamer, is also assessed.

Correlations between low well-being variables and nightmare and unpleasant dream variables

• Correlations between well-being and dream or nightmare variables have age and sex partialled out, and correlations between dream and nightmare variables have sex partialled out. *P < 0.05, **P < 0.01, ***P < 0.001.

Correlations between nightmare and unpleasant dream frequency variables and low well-being variables with nightmare distress partialled out

• All dfs = 99. Sex and age are partialled out. QNF, questionnaire nightmare frequency; ND, nightmare distress; UPDF, unpleasant dreamfrequency. *P < 0.05, **P < 0.01.

Waking Life Well-Being and Nightmares

• Waking life low well-being is related to unpleasant dream frequency and nightmare distress.
• Low well-being may cause unpleasant dreams/nightmares and an adverse reaction to them when they occur.

Nightmares vs. Unpleasant Dreams (Zadra and Donderi, 2000)

• Some researchers believe strictly-defined nightmare frequency (nightmares that wake you up) is more related to low well-being than unpleasant dream frequency.

• NM = nightmare; BD = bad dream; EPI = Eysenck Personality Inventory; STAI-T = State-Trait Anxiety Inventory-Trait; STAI-S = State-Trait Anxiety Inventory-State; BDI = Beck Depression Inventory; SCL = Symptom Checklist 90-Revised; ACL = Adjective Checklist; LEI = Life Events Inventory; WBcomp = well-being composite.
• Correlation coefficients for corresponding measures of nightmare and bad-dream frequency are significantly different at p < .05

Content of Nightmares

• Robert, G., & Zadra, A. (2014) investigated the thematic and content analysis of idiopathic nightmares and bad dreams.
• Nightmares were defined as causing the dreamer to awaken due to the emotions of events in the dream.
• Participants kept a written record of all remembered dreams in a log for 2 to 5 weeks. 9,796 dream reports were collected:
  • 253 nightmares
  • 431 bad dreams
  • 331 participants.
• Physical aggression was the most frequently reported theme in nightmares, whereas interpersonal conflicts predominated in bad dreams.
• Nightmares were rated as substantially more emotionally intense than bad dreams.
• 35% of nightmares and 55% of bad dreams contained primary emotions other than fear.
• Nightmares contained substantially more unfortunate endings compared to bad dreams.

Conclusion (Robert & Zadra, 2014)

• Nightmares are a rarer and more severe expression of the same basic phenomenon of emotionally negative dreams compared to bad dreams.

Sleep Disturbances in PTSD (Brownlow et al., 2015)

• Sleep disturbance is a core feature of PTSD.
• Insomnia and recurrent nightmares are common and distressing symptoms that exacerbate waking symptoms of PTSD.
• 70% of individuals with PTSD report difficulty initiating and maintaining sleep.
• Insomnia symptoms predating the trauma may be a predictor or independent risk factor for PTSD development.

Sleep Apnea and PTSD

• Obstructive Sleep Apnea estimates in general population: 3-7% in men, 2-5% in women.
• 69% of Veterans with PTSD had an apnea-hypopnea index (AHI) >10, indicative of at least mild OSA.

Nightmares and PTSD (Brownlow et al., 2015)

• Self-report: 52-96% of individuals with PTSD experience frequent nightmares (replicative or non-replicative).
• Post-traumatic nightmares within 1 month of a traumatic event predicted greater PTSD symptom severity 6 weeks and 1 year later.

Aetiology of Nightmares (Nielsen & Levin, 2007, 2009)

• Explaining why some people get nightmares.
  Nightmares: A new neurocognitive model

The Affective Network Dysfunction (AND) Model

• Traumatic and stressful events cause fear memories.
• Fear extinction memories are created during dreaming by associating the fear memory with a new non-fearful context or a modified emotional response.
• These processes constitute the fear extinction function of dreaming.
• The theory specifies brain regions underlying these processes:
  • Hippocampus (provides new contexts in the dream).
  • Amygdala (modifies the fear emotion).

Evidence for the AND Model

• Recurrent dreams are emotionally negative, and recurrent dreamers score lower on well-being.
• Levin and Nielsen propose that recurrent dreams occur because the fear memory has not been extinguished.

Affect Distress

• Affect distress is a major determinant of whether a nightmare will constitute a clinical problem.
• Trait or disposition of the tendency to experience distress in response to emotional stimuli/affect load.
• Overlaps with neuroticism (for experiences in general) and trait nightmare distress (for nightmares in particular).

Nightmares and Affect Load

• Bad dreams and nightmares can occur following increased affect load in waking life (e.g., job loss, arguments).
• Occur when the Amygdala is overactive, and the Hippocampus cannot produce sufficiently incompatible contexts to establish or maintain extinction memories.

Post-Traumatic Nightmares

• May occur if there are also traumatic memories; they repeat the traumatic episode and are particularly resistant to feature recombination and extinction.

Adverse Consequences of Nightmares

• Arousal consequences:
  • Increased HR during NM episodes.
  • More eye movements, shorter breath times for high anxiety dreams.
  • Skipping early REM periods, increased REM latency.
  • Increased high alpha spectral power in REM (10–14.5 Hz).
  • Longer sleep latency, more awakenings.
  • More frequent periodic leg movements.
  • More fragmented sleep.
• Nightmares may interfere with sleep function.
• According to Matt Walker, sleep consolidates emotional memory traces but also removes the stress and emotion associated with the memory (Walker & Van der Helm, 2009).

Sleep Disruption and Emotion Regulation

• NM sufferers have higher arousal and decreased medial PFC activity during negative picture viewing (Marquis et al., 2019).
• mPFC is involved in emotion regulation and is less active in high Nightmare Distress individuals, reducing inhibition of the amygdala (Walker & Van der Helm, 2009).

Nightmare Severity and Frontal Brain Activity (Marquis et al., 2019)

• Nightmare severity is inversely related to frontal brain activity during waking state picture viewing.

Executive Functions and Nightmares (Simor et al., 2012)

• Impaired executive functions in subjects with frequent nightmares as reflected by performance in different neuropsychological tasks.
  Simor et al propose that neural background of disturbed dreaming involve impaired prefrontal and fronto-limbic functioning during REM sleep.
• People with this characteristic have difficulty suppressing negative content in dreams.

Possible Functions of Nightmares (Sterpenich et al. 2019)

• Study 1: Fear in dreams associated with activation of fear-related brain areas.
• EEG was used with multiple awakenings during the night.
• Study 2: Those reporting fear in dreams at home had lower brain response and lower pupil response to fear images presented when awake.
• Raises possibility that fear in dreams aids the processing of fear in waking life.
• Study 2 was a correlational study.

Revonsuo’s Threat Simulation Theory

• Fear is represented in nightmares.
• Dreams and nightmares have a behavioural practice rather than extinction or memory function.
• In dreams and nightmares we practice overcoming the circumstances that create fear, similar to virtual reality.

An Evolutionary View of Why Nightmares Occur (Revonsuo, 2000)

• Opposes the view that nightmares (repetitive or not) are a failure of dream function; they aid reproductive success.
• Dreams/nightmares are responses to fear and pain; threat simulation.
• Dreaming is a selective simulation of the world.
• Negative emotions, misfortunes, and aggression are prominent.
  *e.g. on the Hall and Van de Castle, misfortune is 7x as frequent as good fortune, and 45% of dreams have at least one aggressive interaction.
• Children have animal dreams:
  • 39% of the dreams of 4-6 yr olds have at least one animal.
  • Domhoff (1996) found 25-30% of characters in dreams of 2-6 yr olds are animals.
• Hartmann (2000) found reading and writing are mainly absent, walking, talking to friends, and sexual activity are frequent.
• Revonsuo: in dreaming we 'rehearse threat perception and threat avoidance'
• Pain and fear are adaptive; dreams depict 'ancient concerns'; 'default values' are the simulation of 'violent encounters with animals, strangers and natural forces, and how to escape from such situations'
• REM behavior disorder

New Theory on Etiology of Nightmares

• Highly Sensitive Persons are susceptible to nightmares as a result of negative occurences, but can also have positive life outcomes in positive environments
  • Rather than see susceptibility to nightmares as a negative trait, recent work suggests.

NM Sufferers Are Sensitive

*Highly Sensitive Person Scale (Aron & Aron, 1997)
*“Do other people’s moods affect you?”
*“Are you bothered by intense stimuli, like loud noises or chaotic scenes?”
*“Are you deeply moved by the arts or music?”
*Boundary Thinness Scale (Hartmann, 1987)
*“ I am very sensitive to other people’s feelings”
*“ I am unusually sensitive to loud noises and bright lights”
*“When I listen to music, I get so involved it is difficult to get back to reality”

Differential Susceptibility to Nightmares (Carr et al., 2020)

• Highly Sensitive Persons react more to positive and negative environments than do less sensitive persons.
• The study found that High Sensory Processing Sensitivity individuals had a stronger relationship between psychopathology and Nightmare Frequency/Distress than did low SPS individuals.

Treating Nightmares

• Imagery Rehearsal Therapy (IRT) is effective in reducing nightmare distress and frequency.
  *Variations exist in the application od IRT and IRT has also been adapted for use in children suffering from Nighttimes.
• IRT effectively relieves idiopathic, recurrent, and PTSD-related forms of nightmares.
• Decreased psychiatric distress including anxiety, depression, or PTSD symptoms after successful treatment.
• About 70% reported clinically meaningfull improvements in nightmare frequeny.

IRT Principles

• The patient is taught to see the nightmare in terms of poor sleep rather than any trauma.
• Prioritizing sleep de-emphasizes the relationship of nightmares to hyperarousal and