Chapter 14 Candice A. Alfano and Simon Lau Sleep complaints are common in the general population and highly prevalent among individuals seeking mental health services. The most recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association [APA], 2013) categorizes sleep disorders into 10 disorders or disorder groups, including: (1) insomnia disorder; (2) hypersomnolence disorder; (3) narcolepsy; (4) breathing-related sleep disorders; (5) circadian rhythm sleep-wake disorders; (6) non-rapid eye movement (NREM) sleep arousal disorder; (7) nightmare disorder; (8) rapid eye movement (REM) sleep behavior disorder; (9) restless legs syndrome; and (10) substance/medication-induced sleep disorder. Notably, the Sleep-Wake Disorders section included in DSM-5 represent a considerably expanded list in contrast to the previous DSM edition (DSM-IV-TR; American Psychiatric Association [APA], 2000), which included only four broad sleep disorder categories (i.e., primary sleep disorders, sleep disorders related to another mental disorder, sleep disorders related to a general medical condition, and substance-induced sleep disorders). DSM-5 also pays more attention to co-existing conditions, emphasizing the need for sleep-directed clinical intervention even when a comorbid medical or mental disorder is present. These significant changes should be viewed as a direct result of the abundance of sleep-focused research conducted within the past decade. Although mental health researchers and practitioners tend to be most familiar with DSM classifications, the International Classification of Sleep Disorders, second edition (ICSD-2; American Academy of Sleep Medicine, 2005) is commonly used within the field of sleep medicine. The ICSD-2, which is consistent in style with the International Classification of Diseases, 10th edition (ICD-10; World Health Organization, 1994), provides characteristics and diagnostic criteria for over 80 sleep disorders organized into eight broad categories. In addition to a greater breadth of conditions, the ICSD-2 provides information on validated assessments and treatments. Because the intent of this chapter is to review sleep disorders most relevant to the mental health professional (i.e., sleep syndromes that are most likely to present in clinical practice), we limit our focus to DSM-5 sleep-wake disorders likely to be encountered by mental health professionals. Insomnia, hypersomnolence, and narcolepsy are reviewed in the major section titled “Disorders of Inadequate/Excessive Sleep.” The second major section, “Parasomnias,” provides a review of disorders characterized by undesirable motor, verbal, or experiential phenomena occurring in association with sleep, specific stages of sleep, or sleep-awake transition phases. Non-rapid eye movement (NREM) sleep disorders, nightmare disorder, and rapid eye movement (REM) sleep behavior disorder are considered parasomnias. Within both sections, information aimed at assisting clinicians to correctly differentiate these from other sleep disorders, such as those related to a mental disorder, general medical condition, or substance use, are discussed in both sections. Since a fundamental disturbance in brain mechanisms that regulate sleep functions is thought to underlie many sleep disorders (e.g., sleep disorders that cannot be exclusively explained on the basis of a coexisting psychiatric disorder or medical condition), we begin with a brief review of the neuroscience of sleep including the use of polysomnography, considered the “gold standard” for assessing objective sleep patterns. We also provide an overview of actigraphy, which is commonly used in the diagnosis of certain sleep disorders such as circadian rhythm sleep-wake disorders. At a fundamental level, sleep is exemplified by decreased consciousness, decreased responses to external stimuli, and decreased overall motor activity compared to wakefulness. Several brain neuroanatomical structures, genes, and neurotransmitter pathways play a role in sleep; however, no specific neurobiological mechanism(s) have been identified that specifically control the onset, maintenance, or termination of sleep. Electroencephalography (EEG), combined with electrooculography (EOG) and electromyography (EMG), are the basis upon which the two major types of sleep (i.e., rapid eye movement [REM] versus non-REM sleep), sleep staging (non-REM Stages 1–3), and sleep architecture are defined. When electrodes are placed on the head to record surface brain activity, the resultant information is called electroencephalography (EEG). In order to obtain a comprehensive profile of objective sleep, EEG information must be combined with EOG and EMG recordings; these data together are referred to as polysomnography (PSG). EEG brainwaves are defined by amplitude, frequency, and form/shape, all of which are relevant for interpreting stages of sleep. Amplitude refers to the magnitude of the brainwave [from its valley-to-peak (measured in microvolts)]. Frequency is the number of peak-to-peak brainwaves over time [measured in cycles per second, referred to as Hertz (Hz)]. Brainwave frequencies are described using the Greek alphabet: Beta (12–30 Hz), Alpha (8–12 Hz), Theta (4–7 Hz), and Delta (up to 4 Hz). Electrooculography (EOG) measures the movement of the eye. During REM sleep, the phase most commonly associated with dreaming, the eyes move back and forth rapidly. Electromyography (EMG) measures muscle tone and activity. With the exception of the heart, eye, and respiratory muscles, there is a loss of muscle tone in all other major muscle groups during REM sleep. Sleep is divided into two major types: REM and non-REM sleep. The brainwaves of REM sleep are similar or essentially identical to the brainwaves of wakefulness (i.e., low voltage, high frequency). For this reason, REM sleep is often referred to as “paradoxical” or “active” sleep. During the PSG, REM sleep can be distinguished from wake based on the appearance of low-amplitude, high-frequency brainwaves (taking on a “sawtooth” shape/form) in the presence of muscle atonia and rapid eye movements. Non-REM sleep is basically any sleep state that is not REM sleep. Rechtshaffen and Kales (1968) originally defined four stages (I–IV) of non-REM sleep, reflecting lighter-to-deeper stages of sleep. In 2007, the American Academy of Sleep Medicine established a new nomenclature combining non-REM stages 3 and 4 into a single category (non-REM stage 3), commonly referred to as “slow wave,” “deep,” or “delta” sleep. Non-REM Stage 1 (N1) occurs during the transition from wakefulness to sleep. Non-REM Stage 2 (N2), which predominates in adults, is associated with theta waves and the appearance of highly characteristic sleep spindle and K-complex wave forms. Non-REM Stage 3/4 (N3) is the deepest form of sleep. Some patients report dream content during N3 sleep, but such reports are infrequent and reported images are much less vivid as compared to dreams emerging from REM sleep. Sleep architecture refers to the cyclical pattern in the types (REM and non-REM) and stages of sleep. There is a predictable pattern in the progression of REM and non-REM sleep. In healthy normal adults, approximately 15–20 minutes of sleep is required to achieve N2 sleep and approximately 30–60 minutes to transition from N2 to deep sleep (N3). After a period of deep sleep, there is a transition back toward lighter (N2) sleep followed by a period of REM sleep. This cycle, referred to as the ultradian cycle, repeats itself, with progressively longer REM periods throughout the night. Each ultradian sleep cycle lasts approximately 90–120 minutes, with four to five cycles during an 8-hour night. The average proportion of time a healthy adult spends in each of type and stage of sleep is 25% REM and 75% non-REM sleep [N1 (5%), N2 (45%–55%), N3 (15%–25%)]. Abnormalities in the timing, distribution, and/or proportion of different types and phases of sleep are prevalent in various sleep disorders and psychiatric conditions (e.g., depression). The Multiple Sleep Latency Test (MSLT) is a measure of daytime sleepiness, developed by Carskadon and Dement (1997). The test consists of four to five distinct 20-minute sessions, separated by 2-hour intervals, during which the individual is placed in a comfortable, dark sleep environment (i.e., sleep laboratory) and asked to take a nap. The first nap period begins within 3 hours after awakening from the previous night’s sleep. The main purpose of this test is to determine sleep latency and, if present, the presence of REM sleep. Sleep latencies greater than 10 minutes (including an inability to fall asleep) are considered normal in well-rested individuals, whereas people who fall asleep within 5 minutes are judged to be sleep deprived (i.e., suffering from pathological sleepiness). The MSLT is an objective measure of daytime sleep propensity, and the appearance of REM sleep within 20 minutes is suggestive, but not diagnostic, of narcolepsy. Wrist actigraphy is an objective, noninvasive, and relatively cost-effective means of estimating sleep-wake patterns. The small watch-sized device is worn on the nondominant wrist 24 hours a day. Movement data (i.e., activity level sampled at 10-second intervals and summed across 1-minute intervals) is collected and stored over an extended time (up to several weeks) and then used to determine sleep and wake periods. Event markers provide specific information regarding time in bed versus time asleep. Data are then downloaded onto a computer and scored by a computer-generated algorithm reliable in identifying sleep and wake periods. Common variables derived from actigraphy include total sleep time, sleep-onset latency, wake time after sleep onset, and sleep efficiency. In healthy adults, actigraphy-based estimates of sleep correlate well with PSG data, although as sleep becomes more disturbed, actigraphy-based sleep estimates become less reliable (Ancoli-Israel et al., 2003; Kushida et al., 2001). Actigraphy can nonetheless be highly useful in the diagnosis and management of insomnia and circadian-rhythm sleep-wake disorders. The term dyssomnias was formerly used to refer to a broad group of disorders characterized by problems of initiating and/or maintaining sleep or of excessive sleepiness and disturbance in the amount, quality, or timing of sleep. However, this term was eliminated from ICSD-2 in favor of using more specific diagnostic groupings (e.g., ICSD-2 includes Insomnia as its own category and describes 11 different subtypes of the disorder). In the following three sections, we describe specific disorders: insomnia disorder, hypersomnolence disorder, and narcolepsy. The first two are prevalent disorders and highly likely to be encountered by mental health professionals. The last, narcolepsy, is much less prevalent in the general population, but commonly comorbid with affective and other types of psychopathology. Insomnia disorder is largely a subjective complaint of one or more of the following: delayed sleep onset, difficulty maintaining sleep, multiple awakenings from sleep, early morning awakenings, or the failure to feel refreshed after sleeping (i.e., nonrestorative sleep). DSM-5 criteria require at least 1 month of insomnia, as well as secondary impairment in daytime functions (e.g., difficulty concentrating, poor work performance). The sleep difficulty must occur at least 3 nights per week and for at least 3 months. Furthermore, there must be adequate opportunity for sleep. Of note, a change from primary insomnia in DSM-IV to insomnia disorder in DSM-5 was specifically aimed at avoiding primary versus secondary designation when insomnia co-occurs with other psychiatric/medical conditions. Insomnia is the most prevalent of all sleep disorders in the general population. It is also the most common complaint among patients seeking treatment from primary care physicians and mental health professionals. Dissatisfaction with sleep quantity or quality in insomnia disorder may relate to problems falling and/or staying asleep or nonrestorative sleep, and specific symptoms often change across time. Overall, insomnia symptoms are present in approximately 20% of the population and more prevalent in women and older patients. Although it can be an independent condition, insomnia is most commonly observed as a comorbid condition with a medical or psychiatric disorder. Up to 50% of insomnia patients meet criteria for a comorbid mental health diagnosis, most commonly anxiety or depression (Ford & Kamerow, 1989; Ohayon, Caulet, & Lemoine, 1998). Hypersomnolence disorder is characterized by excessive sleepiness for a minimum of 1 month (or less if recurrent). Hypersomnolence is clinically demonstrated either by unusually long sleep episodes or by abnormal amounts of sleeping when the person is expected to be alert. There may be daily episodes of daytime sleep. A person with hypersomnolence disorder sleeps at least 7 hours in a single night and often will sleep 10–14 hours during his or her normal sleeping period. The diagnostic criteria require at least three episodes per week for 3 months and the hypersomnolence must result in functional impairment (APA, 2013). Approximately 5%–10% of patients who seek treatment for excessive daytime sleepiness suffer from hypersomnolence disorder. The disorder is estimated to affect 1% of U.S. and European populations. Males and females are affected equally. The term hypersomnolence broadly includes symptoms of excessive quantity of sleep, deteriorated quality of wakefulness, and sleep inertia (i.e., a period of impaired performance or reduced vigilance following awakening from a regular sleep episode). In extreme cases, sleep episodes can last up to 20 hours. Sleep inertia may last several minutes to several hours. “Automatic behaviors” (i.e., routine, low-complexity behaviors that are poorly recalled later) are commonly reported. Onset is often progressive with a mean age of onset between 15 and 25 years and symptoms worsening over time. Prolonged nocturnal sleep and difficulty awakening in the morning can significantly impair occupational, academic, and personal functioning. DSM-5 distinguishes narcolepsy from other forms of hypersomnolence. Narcolepsy is characterized by excessive daytime drowsiness, emotion-triggered muscle atonia/weakness (i.e., cataplexy), sleep paralysis, and hypnagogic/hypnopompic hallucinations. Narcolepsy is defined as irresistible attacks of refreshing sleep with either one or both of the following: cataplexy or recurrent intrusions of REM-related phenomena such as hypnopompic or hypnagogic hallucinations or sleep paralysis. The severity of sleepiness ranges from feelings of drowsiness while engaged in boring tasks (often requiring naps) to pervasive sleepiness and full-blown sleep attacks. Cataplexy is an interesting phenomenon, with episodes lasting from seconds to minutes. Among individuals with a longstanding disorder, the episodes consist of bilateral muscle tone loss precipitated by laughter or joking (APA, 2013). In children or people with a more recent onset, cataplexy may consist of facial grimacing or jaw-opening or global hypotonia. The prevalence of classic narcolepsy with emotion-triggered cataplexy is approximately 0.02% to 0.05% of the U.S. population, with an equal incidence in men and women. Onset can be abrupt or progressive. Cataplexy, where the atonia/weakness affects the knees, face, neck/head, or muscles of the lower or upper extremities is a pathognomonic of narcolepsy. However, approximately 30% of narcoleptics suffer from excessive daytime sleepiness and sleep-onset REM but putatively have no history of cataplexy. In children and adolescents, cataplexy can be atypical, affecting only discrete muscle groups (e.g., the face). Presence of cataplexy may be a marker of severity and/or low levels of hypocretin. Approximately 20%–60% of narcolepsy patients report sleep paralysis upon falling sleep or awakening. However, sleep paralysis occurs in normal sleepers as well. It is widely known that narcoleptics have trouble staying awake. Less appreciated is that narcolepsy is also associated with insomnia. Thus, patients with narcolepsy have problems with maintaining both sleep and alertness under the appropriate circumstances. Numerous aspects of the narcoleptic patient’s life may be impaired by their symptoms including work/career, travel/driving, socialization and interpersonal relationships. Because narcoleptic patients often appear sleepy, nod off, and/or withdraw from social engagements they are sometimes perceived as lazy, shy, or suffering from a mental disorder. DSM-5 criteria for insomnia and hypersomnolence disorders includes co-occurring medical, psychiatric, and/or other sleep disorders as unique specifiers (rather than exclusions for diagnosis as in DSM-IV). From a clinical standpoint, there is a need nonetheless to determine whether sleep complaints are solely caused by another underlying condition. This is often difficult to determine with certainty since so many disease entities can negatively impact sleep. Within this context, generalized anxiety disorder (GAD) is commonly associated with problems initiating, maintaining, or achieving restful sleep. Insomnia is present in up to 70% of patients with GAD (Alfano & Mellman, 2010; Monti & Monti, 2000) and the quality of insomnia in GAD is nearly identical to that of patients with insomnia disorder. In both insomnia and GAD, patients often worry about obtaining sufficient sleep at night and report difficulty falling asleep and maintaining sleep. Both insomniac and GAD patients report being keyed up (alternating with fatigue) and having difficulty concentrating. Hypersomnolence is common in depressed patients and associations between depression and hypersomnia are likely to be bidirectional. The presence of hypersomnia in major depressive disorder (MDD) has been hypothesized to reflect abnormal sleep homeostasis in depressed patients. Persistence of hypersomnolence after depressive symptoms have been adequately treated may signal risk for recurrent depression (Breslau, Roth, Rosenthal, & Andreski, 1996; Roberts, Shema, Kaplan, & Strawbridge, 2000). A diagnosis of Kleine–Levin syndrome should be considered among hypersomnolent patients. This neurological disorder is characterized by recurring periods of hypersomnolence lasting several weeks to several months. These individuals demonstrate largely normal cognitive, emotional, and behavioral functions between episodes. Patients with Kleine-Levin hypersomnia often demonstrate compulsive eating (polyphagia), inappropriate sexuality (e.g., public masturbation), or other bizarre behaviors during episodes. Patients with recurrent hypersomnia are much more likely to demonstrate neurological problems such as impaired memory, gait disturbances, and autonomic nervous system dysfunctions (e.g., sweating, flushing, low blood pressure, and bradycardia) (Billiard, Jaussent, Dauvilliers, & Besset, 2011). Breathing-related sleep disorders (i.e., obstructive sleep apnea) must also be ruled out. These are serious conditions that, when left untreated, lead to impaired memory and work performance, poor motor coordination, poor executive functions, and health risks. Risk factors are obesity, large neck circumference (> 17 inches), increasing age (over 40% in the elderly), male gender, positive family history, or any medical condition that obstructs or impairs the patency of the upper airway. However, normal or even underweight individuals can be diagnosed with obstructive sleep apnea. Although PSG is required to diagnose a breathing-related sleep disorder, excessive daytime sleepiness, loud snoring or gasping during sleep, dry mouth upon waking, and recurrent headaches are cardinal features. Narcolepsy commonly co-occurs with depressive symptoms. A precise causal relationship remains unclear but bidirectional associations are suggested. For example, hypocretin deficiency, through a cholinergic–monoaminergic imbalance, is linked with dysregulation of mood (Dauvilliers, Lopez, Ohayan, & Bayard, 2013). Like narcoleptics, patients with MDD or patients in the depressed phase of bipolar disorder commonly experience fatigue and excessive daytime sleepiness. Mood disorders also can be associated with psychosis, and hypnagogic/hypnopompic hallucinations associated with narcolepsy may be interpreted as psychotic symptoms. Because circadian rhythm sleep-wake disorders include problems remaining alert or sleeping at appropriate times, differentiation from disorders of inadequate or excessive sleep should be made. DSM-5 recognizes three subtypes of circadian rhythm sleep-wake disorders including delayed sleep phase type (most common in adolescents), advanced sleep phase type (most common in older and geriatric patients), and irregular sleep-wake type. The essential characteristic of these disorders is a misalignment between the required/desired sleep schedule and natural biological rhythms. Individuals with restless legs syndrome have symptoms (e.g., creepy-crawly feelings in the legs) that commonly interfere with sleep. There are clear-cut urges to physically get up and move around, which temporarily reduces “tension” in the legs. A high proportion (up to 75%) of patients with restless legs syndrome develop repeated limb movements in sleep, which are characterized by muscle twitches and jerks every 20–40 seconds throughout the night. Since restless legs syndrome is commonly associated with sleep-related periodic limb movements (PLMs), insomnia and hypersomnia complaints are common since movements may occur hundreds of times throughout the night and disrupt sleep. Polysomnography (PSG) is not generally used as a tool in the diagnosis of insomnia. No objective findings on PSG (e.g., sleep architecture, proportion of time in sleep stages) are specific to insomnia. Subjective sleep logs and/or actigraphy are commonly used; however, there is lack of consensus regarding quantitative criteria for identifying insomnia. Somewhat arbitrarily, difficulty initiating sleep is often defined by subjective sleep latency of greater than 20–30 minutes, whereas difficulty maintaining sleep has been defined by subjective time awake after sleep onset greater than 20–30 minutes. Research has suggested that a useful combination of actigraphic sleep parameters to assess insomnia include total sleep time, sleep onset latency, and number of awakenings longer than 5 minutes (Natale, Plazzi, & Martoni, 2009). In hypersomnolent patients, the PSG will typically show decreased sleep latency, increased total sleep time, and normal (or increased) sleep efficiency. The amount of time in deep sleep may be increased. The average MSLT sleep latency is short (<5 minutes). Kleine-Levin hypersomnia is associated with increased sleep propensity on MSLT. A distinctive PSG feature of narcolepsy is sleep-onset REM. The first REM period in healthy individuals takes place about 90 minutes after sleep onset. In patients with narcolepsy, the first REM period often takes place in less than 20 minutes or, in some cases, “the moment the head hits the pillow”; thus, the term sleep-onset REM. Sleep-onset REM also may take place during daytime naps, particularly in those narcoleptic patients with sleep deprivation. Although the presence of sleep-onset REM on the MSLT is highly suggestive of narcolepsy, it is not a definitive confirmation of the disorder (Mignot et al., 2002). Since most narcoleptic patients are hypocretin deficient (i.e., low levels or the absence of hypocretin in CSF) (Mignot et al., 2002), measuring CSF hypocretin-1 is considered a definitive diagnostic test. It is often most useful in cases where MSLT findings are difficult to interpret. If there are no identified mechanical blockages (e.g., enlarged tonsils or craniofacial abnormalities) or endocrine disorders, continuous positive airway pressure (CPAP) is the treatment of choice for obstructive sleep apnea. CPAP is highly effective but associated with poor compliance, which can be attributed to the cumbersome and noisy nature of the equipment. Concomitant cognitive-behavioral or motivational interventions may be successful in improving CPAP compliance problems. There is no diagnostic test for circadian rhythm sleep-wake disorders. A history of external changes in the timing of sleep in conjunction with a sleep log or actigraphy makes it fairly easy to identify circadian disorders. Individuals with a delayed sleep phase almost always report having extreme difficulty waking in the morning, whereas the individual with an advanced sleep phase will report difficulty maintaining wakefulness during the evening hours. The diagnosis of restless legs syndrome is made on the basis of history and ruling out other possible medical or neurological diseases. Talking with the patient’s bed partner is valuable, because this person will inevitably report extreme restlessness throughout the night, which is easily confirmed by polysomnography. Patients with restless legs syndrome often meet ICSD-2 criteria for periodic limb movement disorder (PLMD), which can be confirmed with overnight PSG.
Sleep-Wake Disorders
Introduction
Neuroscience of Sleep
Polysomnography (PSG)
Types of Sleep
Sleep Stages
Sleep Architecture
Multiple Sleep Latency Test (MSLT)
Actigraphy
Disorders of Inadequate/Excessive Sleep
Insomnia Disorder
Epidemiology and Other Features
Hypersomnolence Disorder
Epidemiology and Other Features
Narcolepsy
Epidemiology and Other Features
Diagnostic Considerations
Psychological and Biological Assessment
Etiological Considerations
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