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In Neuropsychology, Neuroscience, Psychiatry, Psychopharmacology on Tuesday, 23 October 2012 at 09:51

What Physicians Need to Know about Dreams and Dreaming

James F. Pagel

Abstract

Purpose of review: An overview of the current status of dream science is given, designed to provide a basic background of this field for the sleep-interested physician.

Recent findings: No cognitive state has been more extensively studied and is yet more misunderstood than dreaming. Much older work is methodologically limited by lack of definitions, small sample size, and constraints of theoretical perspective, with evidence equivocal as to whether any special relationship exists between rapid eye movement (REM) sleep and dreaming. As the relationship between dreams and REM sleep is so poorly defined, evidence-based studies of dreaming require a dream report. The different aspects of dreaming that can be studied include dream and nightmare recall frequency, dream content, dreaming effect on waking behaviors, dream/nightmare associated medications, and pathophysiology affecting dreaming.

Summary: Whether studied from behavioral, neuroanatomical, neurochemical, pathophysiological or electrophysiological perspectives, dreaming reveals itself to be a complex cognitive state affected by a wide variety of medical, psychological, sleep and social variables.

Introduction

As most individuals experience the cognitive mentation that we call dreams during sleep, any physician treating sleep needs to have at least a basic understanding of dreaming. It was just 50 years ago that polysomnography allowed for sleep to be electrophysiologically staged. Although sleep had yet to be examined, a huge literature existed on dreaming and, through psychoanalysis, the use of dreams in the treatment of the spectrum of mental illness. Today, the scientific study of dreams has come full circle. We now know a huge amount about sleep, its associated pathophysiology, and treatment, yet what we know scientifically about the dream state is far less than what we thought we knew a generation ago. Much older work was not evidence based, and was methodologically limited by lack of definitions, small sample size, and the constraints of theoretical perspective. After 50 years of dogmatic insistence that rapid eye movement (REM) sleep is dreaming, most researchers in the field now accept that the evidence is overwhelming that REM sleep occurs without dreaming and dreaming without REM sleep.[1] Evidence remains equivocal as to whether any special relationship exists between REM sleep and dreaming.[2•] It is unclear as to what part, if any, of the highly developed neuroanatomical and neurochemical model for REM sleep is applicable to the cognitive state of dreaming.

Definitions: What is a Dream?

Early in the 20th century, Sigmund Freud and his adherents developed the psychoanalytic techniques of free association and dream analysis for use in diagnosing and treating individuals with psychiatric illnesses. Freud focused on the psychopathologic associations of bizarre and unusual dreams, eventually giving us a definition of dreaming as ‘wish fulfillment.’ Psychoanalysts stretched the definition of dreaming to include parasomnias and the REM sleep-associated states of narcolepsy, defining dreams as bizarre, hallucinatory mental activity that can occur in either sleep or wake.[3] This psychoanalytic definition of dreaming became the generally accepted definition for this phenomenon among many psychiatrists and neuroscientists.

From its initial discovery, REM sleep = dreaming was proof of the correlate between psychoanalysis and brain structure, a postulate at the basis of grand theories of dreaming including Activation, Input, Modulation (AIM), now termed protoconsciousness theory and the most developed and widely accepted theory of central nervous system (CNS) functioning.[4] It is a primary postulate of AIM that the neurons and neurochemicals that modulate REM sleep alter dreaming and other conscious states in a similar manner. The AIM model has been adopted and extended into proposals that REM sleep dreaming is the process that organizes neural nets in higher cortical regions.[5] These theories postulate that the cognitive activity of dreaming is based on the CNS activation associated with REM sleep, with dreaming an upper cerebral cognitive process utilizing the CNS activation associated with a primitive electrophysiological state of activation that we call REM sleep. If REM sleep is dreaming, animal models and scanning studies of REM sleep as reported in the popular and scientific press can be construed to be studies of the cognitive state of dreaming. Such studies must be considered suspect, however, as dreaming occurs throughout sleep in forms (except for nightmares) indistinguishable from REM sleep dreaming.[6]

Most sleep medicine physicians consider dreaming to be mentation reported as occurring in sleep by a human participant. This definition contradicts the psychoanalytic definition for dreaming, restricting dreaming to sleep irrespective of content. This definition also differs from the REM sleep = dreaming model in requiring a dream report. Because of this conflation of contradicting definitions, it is important for anyone interested in perusing either scientific or popular literature to note what the author may be referring to in any discussion of dreams and dreaming.[7]

Evidence-based Research Into Dreaming

Characteristics of the dream state amenable to scientific study include recall, content, dream incorporation into waking, and associated pathophysiology.

Dream Recall

Collection methodology including time since waking, process, and defined state characteristics affect reported dream recall frequency. Sleep stage of origin is a primary variable known to affect dream recall frequency. Multiple studies indicate that dream recall reported from REM sleep and sleep onset is in the range of 80%. Although recall from stage 2 varies through the night, recall approximates the 40% recall from stage 3.[8] Recall is generally higher for women and in the young.[9] Increased dream salience and intensity, typical of nightmares, also results in an increase in recall. Significant subjective and objective insomnia is associated with diminished dream recall.[10] Bi-basilar frontal CNS damage can be associated with a loss of dreaming.[11] Although some individuals report that they do not dream, most have experienced dreams at some point in their lives. The much smaller percentage of sleep laboratory patients that have never experienced dreaming (0.038%) do not report dreams in the laboratory when awakened from either REM sleep or non-REM sleep.[12] Despite their lack of dream recall, these individuals have no obvious memory impairment and function normally in our society.

Dream Content

Guttenberg’s first printed book was the Bible, but his second was the Oneirocritica, an interpretation of the meaning of dream symbols.[13] Mankind’s focus on dream content likely predates the development of either printing or writing.[2•] Dream content has been incorporated into the worlds’ major religions, philosophies, literature, and science. The argument can cogently be made that the structure and narrative form of language itself is derived from our attempts to organize and share our dreams. Most dreams are narratives occurring, and often presented without applied organization, grammar, or expectation of critique. In the dream, we can literally observe the ‘thinking of the body,’ and with it, the birth of the literary process. Our dreams can be considered an exercise in pure storytelling whose end is nothing more (or less) than the organization of experience into set patterns that help to maintain order for the thinking system.[14]

Freud postulated that an individual’s psychic structure could be inferred from information derived from the associative interpretation of dreams, and then could be utilized in developing a therapeutic plan for the treatment of psychiatric symptoms.[15] He stated, ‘Psychoanalysis is related to psychiatry approximately as histology is related to anatomy’.[16] For more than a generation, psychiatrists were trained in the method, with the data derived from psychoanalytic techniques used to make diagnoses and form treatment plans. Although psychoanalysis was utilized with occasional success in treating psychiatric illness, most of the evidence attesting to its therapeutic efficacy was anecdotal and subjective.[3]

More recent studies of dream content have attempted to address the significant methodological problems of transference, collection and interpretation that led to the nonreplicable characteristics of dream content studies. Methodologically sound studies have been developed that utilize computerized analysis of the validated Hall and Van de Castle content system.[17] Such studies have shown few, if any, significant differences in dream content between personality types, psychopathologic diagnoses, or socio-ethnic groups.[18] The primary significant correlate for dream content has proven to be waking experience, supporting the so-called continuity hypothesis – dream content reflects our waking experience.[18] Dream researchers have persisted in developing alternative content scales in order to support theoretical perspectives.[19] Although few of these scales have been validated or subjected to independent analysis, the best data is for Hartmann’s analysis of personality correlates (boundaries) that affect both dream recall frequency and content.[20]

Studies have also started to address other aspects of dream content. Visual imagery, the primary characteristic of most reported dreams, follows an operative pattern in dreaming that can be studied and applied externally to filmmaking methodology.[6] Memories follow characteristic patterns in both dream-associated sleep and varied waking states.[21•] Emotions, particularly negative emotions, are routinely incorporated into dreaming.[22]

Dream Incorporation Into Waking Behavior

Many individuals use their dreams. As in recall, dream-use tends to be sex-based and age-based (higher in women and the young).[23] Although ethnic and cultural differences in dream-use exist, such variations do not tend to be present in general population samples.[24] Dream use is significantly higher among individuals reporting creative interests.[25] Among successfully creative individuals, dream and nightmare recall, as well as dream incorporation into work and waking behavior is much higher than in the general population, suggesting that one function of dreaming may be in the creative process.[6,26]

Medications Inducing Disturbed Dreaming and Nightmares

Until recently, neurochemists interested in dreaming focused their studies on the effects of various neurochemicals on REM sleep based on the belief that medications affecting dreaming would be the same ones known to affect REM sleep. Acetylcholine is the primary neuromodulator affecting REM sleep.[27] A wide variety of pharmaceutical agents have anticholinergic activity, and the reported side effects of some of these agents include nightmares, disordered dreaming and hallucinations. This has led some authors to postulate that cholinergic effects of medications induce nightmares, hallucinations, and psychosis.[28] Based on this theoretical construct, the anticholinesterase agents in widespread use for the treatment of the cognitive effects of Alzheimer’s disease should alter dreaming. These agents, however, are reported to induce the side effect of disturbed dreaming or nightmares in only 0.4% of clinical trial participants.[29]

Agents that suppress REM sleep such as ethanol and benzodiazepines induce episodes of REM sleep rebound on withdrawal. These REM sleep rebound episodes have been associated with reports of nightmares and disturbed dreaming, and were considered the primary mechanism for drug-induced disordered dreaming and nightmares. However, nightmares and disordered dreaming are often reported as part of the withdrawal syndrome from addictive medications such as cannabis, cocaine and opiates that, which are not known to affect REM sleep. This suggests that during withdrawal from addictive agents, disturbed dreaming and nightmares may be an intrinsic part of that process rather than occurring secondary to REM sleep rebound.[29,30]

Data based on clinical trials and case reports of effects and side effects of clinically utilized pharmaceutical agents indicate that a much different pattern of medications induce disordered dreaming and nightmares than those known to affect REM sleep.[29] The spectrum of medications affecting dreaming indicates that the state is neurochemically complex with medications influencing the neurotransmitters/neuromodulators dopamine, nicotine, histamine, GABA, serotonin, nicotine, and norepinephrine altering dreaming and reported nightmare frequency in 1–5% of patients using these medications.[29] Medications with clinical cognitive effects and/or side-effects of arousal (insomnia) and/or sedation are those that most commonly alter the reported frequency of disordered dreaming and nightmares ( ).

Among drug classes of prescription medications in clinical use, β-blockers affecting norepinephrine neuroreceptors are most likely to result in patient complaints of disturbed dreaming. The strongest clinical evidence for a specific drug to induce disordered dreaming or nightmares is for the selective serotonin reuptake inhibitor paroxetine – a medication known to suppress REM sleep. Because of the high frequency of use of over-the-counter preparations containing type-1 antihistamines for sleep induction and the treatment of allergies, such preparations are likely responsible for most reports of drug-induced disordered dreaming and nightmares.[29]

Table 1.  Cognitive effects and side effects of medications: neurotransmitter/neuromodulator-associated central nervous system effects

Basis for central nervous system activity Sleepiness Insomnia Alterations in dreaming
Neuromodulator and/or neurotransmitter mediated effects
   Serotonin +++ ++ +++
   Norepinephrine ++ ++ +++
   Dopamine +++ +++ +++
   Histamine +++ + ++
   GABA +++ + ++
   Acetylcholine ++
   Adenosine + +++
   Nicotine +++ +++
Other medication effects
   Effects on inflammation ++ ++ ++
   Addictive drug withdrawal + +++ +++
   Altered conscious interaction with environment +++ + ++
   Alterations in sleep associated disease +++ +++ +

+++, majority of drugs with this activity cause this effect in more than 5% of patients; ++, some drugs with this activity induce this effect in 1–5% of patients; +, an idiosyncratic effect for some agents in this group or withdrawal effect; −reported in less than 1% of patients using agents affecting this neurotransmitter/neuromodulator [29]

Pathophysiology of Dreaming And Nightmares

Although changes in dreaming are sometimes reported, most reports of pathophysiological correlates for dreaming are reports of nightmares – coherent dream sequences usually occurring in REM sleep that become increasingly more disturbing as they unfold and usually resulting in awakening.[31]

Dream-like Parasomnias

Dreaming (cognitive narrative, feeling, or awareness of dreaming on awakening) occurs in association with many parasomnias – unwanted behaviors occurring during sleep.

Parasomnias are in general classified based on sleep stage of origin.

Disorders of Arousal

The disorders of arousal occurring out of deep sleep are associated with dream mentation up to 40% of the time. Somambulism is characterized by autonomic and inappropriate behaviors, frantic attempts to escape a perceived threat, and fragmentary recall. Sleep terrors and confusional arousals are associated with incoherent vocalizations, intense autonomic discharge, confusion and disorientation, and fragmentary dream recall.[32]

Hypnogognic Phenomena

The sleep onset nightmares typical of posttraumatic stress disorder (PTSD) and sleep onset sleep paralysis can occur without the classic REM sleep association. Sleep onset PTSD nightmares often induce distress that interferes with the initiation of sleep. Hypnogogic hallucinations are primarily visual and have coherent dream storylines that are perceived as potentially real. Although commonly experienced (prevalence rates vary from 25 to 37%), such experiences are also a part of the classic tetrad of narcolepsy.[33] The regularly experienced hypnogogic hallucinations reported by 40–60% of individuals carrying the diagnosis of narcolepsy with cataplexy may have more complex storylines than those reported in the general population.[3,34] Sleep starts, most commonly experienced at sleep onset, can be associated with the impression of falling.

Rapid Eye Movement Sleep-associated Parasomnias 

REM sleep is classically associated with dream-like parasomnias. Some of these parasomnias can also occur outside REM sleep. PTSD nightmares and sleep paralysis can occur at sleep onset. REM sleep behavior disorder (RBD) phenomena can also occur in association with arousal disorders.

Nightmare Disorder

Nightmare disorder is characterized by recurrent nontrauma-related REM sleep dreams that result in intense anxiety, fear or terror, and a coherent dream story usually involving imminent physical danger for the dreamer. Associated insomnia and difficulty returning to sleep are usually present. As in most parasomnias, arousals associated with obstructive sleep apnea (OSA) or periodic limb movement disorder can result in increased symptomatology; however, in patients with the disordered sleep associated with moderate to severe OSA, normal dreaming is maintained while reported nightmares actually decline in frequency.[35] Personality patterns typically present in individuals with frequent nightmares include fantasy proneness, psychological absorption, dysphoric daydreaming and ‘thin’ boundaries.[20] Such individuals are more likely to have a creative or artistic focus in their daily lives. Some of these individuals may utilize their dreams and nightmares in highly successful creative careers in writing, acting and film.[36 

Posttraumatic Stress Disorder-associated Nightmares

Frequent nightmares are the most common symptom of PTSD, affecting approximately 25% of individuals who have experienced severe emotional or physical trauma.[37] The nightmares that characterize PTSD are frightening and sometimes stereotypic dreams that can include re-experiencing of the individual’s trauma. Nightmares may be a failure of emotional processing systems that are active during sleep, particularly REM sleep.[22,38] Significant improvement in both sleep onset and maintenance insomnia has been achieved in PTSD patients with the use of both cognitive/behavioral and medication approaches that demonstrably reduce the frequency and distress associated with these disturbing dreams.[39]

Rapid Eye Movement Sleep Behavior Disorder (RBD) and Sleep Paralysis

In patients with RBD, vivid dreams are often ‘acted out.’ Such dream-related behavior can be violent and can result in injury to the victim or bedpartner. In contrast to those who experience sleep terrors, the victim will often recall coherent dream stories that, in a minority of cases, correlate with observed RBD behaviors.[40] RBD events can occur outside the sleep stage for which it is named.[41] During REM sleep associated with sleep paralysis, the inability to perform voluntary movements on waking, with full recall of dreaming, can lead to intense anxiety.

Other Dream-like Parasomnias

Sleep talking (somniloquy), which usually occurs in stage-2 non-REM sleep but which can accompany any stage of sleep, may include embarrassing waking content. Anxiety and panic attacks, also predominately occurring in stage-2, may also include coherent dream content. Sleep related dissociative disorder occurring in individuals with waking dissociative disorders is characterized by re-experiencing of trauma that presents during nighttime awakenings. Nocturnal partial epileptic seizures can include thoughts and hallucinations.[42]

Conclusion 

The recent progress that researchers have made in understanding dreams has been incremental, and is not nearly as exciting as the simplified insights, at the time regarded as breakthroughs into the process of consciousness, that were once attributed to dreaming. This recent work indicates that dreaming is a complex cognitive state whether viewed from behavioral, neuroanatomical, neurochemical, pathophysiological or electrophysiological perspectives. Our dreams are what we remember in the morning of the cognition taking place in our CNS during sleep. It is recommended that physicians treating sleep and its disorders be familiar with current knowledge of the science of dreaming. 

Sidebar

Key Points

  • Dreaming is not limited to rapid eye movement (REM) sleep, but rather occurs throughout sleep.
  • Dreaming defined as cognitive narrative, feeling, or awareness of dreaming on awakening occurs in association with many parasomnias.
  • Dreaming is a complex cognitive state whether viewed from behavioral, neuroanatomical, neurochemical, pathophysiological or electrophysiological perspectives.
  • Medications affecting the neurotransmitters/neuromodulators dopamine, nicotine, histamine, gamma-aminobutyric acid (GABA), serotonin, nicotine, and norepinephrine alter dreaming and reported nightmare frequency.

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Curr Opin Pulm Med. 2012;18(6):574-579

Retrieved from: http://www.medscape.com/viewarticle/772192_2

 

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