Sleep Disturbances Associated With Posttraumatic Stress Disorder

Abstract

Sleep disturbances, namely insomnia and recurrent nightmares, are ubiquitous following trauma exposure and are considered hallmarks of posttraumatic stress disorder (PTSD). Other sleep disorders frequently co-occur with PTSD. This article describes research examining sleep problems most common in PTSD, including prevalence and clinical characteristics. Sleep disturbances are often robust to trauma-focused treatment; thus, evidence for psychological and pharmacological interventions for insomnia and nightmares in PTSD are discussed. Given the high prevalence of sleep problems in PTSD, more work is needed to empirically study putative mechanisms linking trauma exposure and sleep, as well as how to best target these symptoms in patients with PTSD.

Sleep disturbance is highly prevalent in posttraumatic stress disorder (PTSD), with upwards of 90% of those with the disorder endorsing some form of sleep problem.¹ In fact, sleep disturbance has been described as a hallmark of PTSD. Recurrent nightmares and difficulty initiating and/or maintaining sleep (ie, insomnia) are embedded within two distinct symptom clusters in the diagnostic criteria for PTSD: nightmares as a “re-experiencing” symptom and insomnia as a “hyperarousal” symptom.² Additionally, sleep disturbance is more prevalent in those with PTSD than without.³ However, sleep difficulties often do not remit following the successful completion of evidence-based treatment for PTSD.⁴ Given that sleep disturbance is a risk factor for the development and persistence of PTSD symptoms, trauma-related sleep problems warrant targeted clinical intervention.

INSOMNIA

Insomnia, broadly defined as difficulty initiating and/or maintaining sleep, is the most common sleep complaint following trauma exposure¹ and in those diagnosed with PTSD, with rates of approximately 70% in diagnosed individuals.³ Trauma-induced insomnia is thought to be a result of hyperarousal following exposure to a traumatic event and often causes clinically significant distress or impairment in functioning, even if the full diagnostic criteria for insomnia disorder are not indicated (see the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, text revision [DSM-5-TR]² for definition and diagnostic criteria for insomnia disorder). Although insomnia disorder is also commonly conceptualized as a disorder of hyperarousal, studies comparing sleep disturbances in those with comorbid PTSD and insomnia versus insomnia disorder alone have shown that patients with PTSD and insomnia had worse subjective sleep quality, more fragmented sleep, and greater variability (ie, less consistency) in night-to-night sleep.⁵

Heightened vigilance and associated sleeplessness are adaptive parts of the acute stress response following exposure to traumatic or highly stressful events and is aptly dubbed “sleep reactivity”; however, sleep reactivity in excess can predispose individuals to develop clinically significant symptoms of insomnia. Therefore, receiving inadequate sleep in the aftermath of trauma is likely a significant risk factor for worse psychological outcomes. Interestingly, one study observed that both too little and too much sleep immediately following a traumatic event was associated with more severe PTSD symptoms,⁶ which suggests that aberrant sleep more broadly (ie, deviations from the norm) may signify poorer trauma trajectory. In general, insomnia been identified as an important risk factor for the development of PTSD, where longitudinal studies have shown that insomnia symptoms prior to exposure to a traumatic event⁷ and following trauma exposure⁸ independently increase the risk of subsequent psychiatric symptoms, including PTSD. Altogether, these findings highlight the important role of healthy sleep in processing emotionally charged content and mitigating long-term psychological consequences.

NIGHTMARES

While insomnia appears in diagnostic criteria for several other mental health disorders, such as mood and anxiety disorders, recurrent nightmares are specific to trauma-related disorders. The PTSD criteria specify that the content or affective tone must be related to the traumatic event.² Reported prevalence rates for posttrauma nightmares vary considerably, ranging from 19% to 96%,⁹ which is due to several factors including differences in nightmare definitions (eg, whether individuals need to awaken in order for it to be considered a nightmare), types of assessment (eg, interview versus self-report), and the population of interest (eg, men versus women, civilian versus military). Nonetheless, rates for trauma-related nightmares in the general population appear to be significantly higher than those of idiopathic (ie, with no known cause) nightmares.² Although trauma-related nightmares are distinguishable from idiopathic nightmares in that they must be related to the trauma either in content/themes or valence, they can vary in the extent to which they are replicative of the traumatic event. Several studies have noted associations between nightmare similarity and PTSD severity, such that the more similar or replicative a nightmare is to the traumatic event, the more severe the PTSD symptoms tend to be.¹⁰ Replicative nightmares are also associated with higher nightmare frequency, greater distress related to nightmares, and worse overall sleep quality.¹⁰

Most dreaming occurs in rapid eye movement (REM) sleep, but surprisingly posttrauma nightmares can arise in both REM and non-REM sleep. Although it was commonly thought that nightmares that occur during REM sleep are more replicative in nature, a recent study did not observe any patterns between sleep stage and nightmare content.¹¹ Physiological correlates of nightmares in general have been difficult to identify, given that they are infrequently reported when in a sleep laboratory setting,¹² but some studies have noted physical characteristics consistent with dysregulated arousal modulation, including increased heart rate prior to awakening from a nightmare,¹¹ muscle activity,¹¹ and respiratory events.¹³ In addition to more severe PTSD symptoms, chronic nightmares are associated with other adverse outcomes including depression and have been identified as a risk factor for subsequent suicidal behaviors independent of comorbid psychiatric symptoms.¹⁴ This highlights nightmares as a critical and modifiable symptom for mitigating adverse outcomes, particularly in those with PTSD who are more likely to experience more frequent and distressing nightmares.

OTHER SLEEP DISORDERS AND PTSD

Beyond the sleep symptoms specified in the PTSD diagnostic criteria, other sleep disorders are also often comorbid with PTSD. Obstructive sleep apnea (OSA) is a form of breathing-related sleep disorder characterized by repeated complete (apneas) or partial (hypopneas) upper airway obstruction during sleep, often initially identified through snoring and daytime sleepiness.² These obstructions are quantified via the apnea-hypopnea index (AHI), which determines the severity of OSA by the number of oxygen desaturation events per hour. Due to the disruption to breathing during sleep, OSA leads to microarousals and fragmented sleep. Several studies have reported that patients with PTSD are at high risk for OSA, with a recent meta-analysis indicating pooled prevalence rates ranging between 43.6% to 75.7% based on different AHI criteria compared to 5% to 15% in the United States (US) adult population.^2,15 Additionally, greater PTSD symptom severity appears to increase risk for OSA.¹⁶ If left untreated, OSA increases risk of morbidity and mortality (eg, cardiovascular events, stroke, diabetes) and may compromise the effectiveness of PTSD treatment.¹⁷ While specific mechanisms linking PTSD and OSA are not certain, a bidirectional relationship has been posited such that posttraumatic stress increases lighter, more fragmented sleep, which leads to increased likelihood of upper airway collapsibility and further fragments sleep.¹⁸ Treatment of OSA in those with comorbid PTSD and OSA appears to also improve PTSD symptoms, but this population may be less likely to be adherent to the treatment.¹⁷ Because common predictors of OSA, including body-mass index and age, may not be as applicable in patients with PTSD,¹⁶ comprehensive screening for OSA should be routinely completed as a part of assessing PTSD, and sleep medicine providers should make efforts to mitigate nonadherence to sleep apnea treatment, particularly in patients with PTSD.

Polysomnography abnormalities in patients with PTSD are most notable in REM sleep. REM sleep, which is generally associated with vivid dreaming, is characterized through polysomnography by quick eye movements and muscle atonia. Patients with PTSD exhibit increased density of eye movements (ie, higher frequency of eye movements) and motor activity during REM.^19,20 Disruptions in skeletal muscle atonia during REM leads to an individual acting out their dreams and may be indicative of rapid eye movement sleep behavior disorder (RBD). Prevalence rates of RBD in the general population are estimated to be between 0.5% to 2%.² However, as with OSA, RBD is reported to be higher among patients with PTSD at 9%.²¹

Mysliwiec and colleagues proposed a novel parasomnia called trauma-associated sleep disorder (TSD) that is characterized with traumatic event exposure and nightmare enactment associated with physiological indicators (eg, REM sleep without atonia, disruptive nocturnal behaviors, sympathetic activation).²² The authors proposed this sleep condition with the rationale that sleep disturbances precipitated by trauma exposure have long been described as fundamentally different than other forms of sleep disturbances, warranting discrete clinical recognition.²² For instance, although TSD has overlapping clinical features with RBD and nightmare disorder, the clinical presentation of TSD occurs in close temporal proximity to the traumatic event, which is inconsistent with RBD, and nightmare disorder is not typically accompanied with dream enactment.²² TSD is also distinguishable from PTSD by including dream enactment as an explicit characteristic of the disorder, whereas the diagnostic criteria for PTSD only specify insomnia and nightmares.²² TSD has yet to be codified in any mental disorder classification system, but the proposed diagnostic criteria for this disorder have been published.²²

CLINICAL TREATMENTS FOR TRAUMA-RELATED SLEEP DISTURBANCES

Sleep disturbances often do not remit following trauma-focused treatment, despite improvements in PTSD symptoms, suggesting that sleep symptoms warrant targeted intervention. Several organizations, including the US Department of Veterans Affairs, publish clinical practice guidelines reviewing various psychological and pharmacological treatments for PTSD.²³ However, consensus guidelines that specifically address sleep problems in patients with PTSD are needed. In a recent review of the literature, Colvonen and colleagues outline a methodological overview for the assessment and psychological treatment of sleep problems in PTSD.¹⁷

Psychological interventions for sleep are based on cognitive-behavioral strategies to target maladaptive processes that affect sleep quality. For insomnia, cognitive-behavioral therapy for insomnia (CBTi) is considered a “gold-standard” treatment that includes a combination of stimulus control (ie, using the bed for sleeping only), sleep restriction (ie, limiting time in bed to patients’ actual sleep duration), cognitive restructuring, and sleep hygiene education (ie, general recommendations about healthy sleep habits). Several studies have shown the efficacy of CBTi on improving sleep in samples with comorbid psychiatric conditions, including PTSD, with a meta-analysis showing large effect sizes in sleep outcomes and smaller improvements in PTSD outcomes.²⁴ Sleep variables that demonstrated improvements included sleep onset latency (ie, decreased time to initially fall asleep), wake after sleep onset (ie, decrease in minutes spent awake after initial sleep onset), and sleep quality.

In terms of nightmares, the most widely studied psychotherapy is a cognitive-behavioral therapy for nightmares (CBT-N), which generally consists of sleep psychoeducation, rescripting (ie, having a patient rewrite a nightmare to be nondistressing) with rehearsal throughout the day, and relaxation training. The Department of Veterans Affairs and the American Psychological Association do not make specific recommendations for treatments of trauma-related nightmares, citing insufficient evidence.²³ However, like CBTi, several studies have shown large effect sizes in nightmare reduction and improved overall sleep quality (see Casement and Swanson²⁵ for a meta-analysis). Additionally, CBT-N exhibited large decreases in global PTSD symptoms, though perhaps was not as effective as PTSD-specific treatments.²⁵ Combined CBTi plus CBT-N appears to be advantageous for sleep but not for nightmares or PTSD, interestingly. Despite encouraging findings, more research is needed to determine treatment factors specific to CBT-N, such as ideal patient population and mechanisms of change, in order to ultimately inform good clinical practice guidelines.

Pharmacological treatment for sleep problems encompasses several classes of medications, including selective serotonin reuptake inhibitors (SSRIs), typical/atypical antipsychotics, and alpha-1 adrenergic receptor antagonists. Although SSRIs and serotonin-norepi-nephrine reuptake inhibitors (SNRIs) are considered first-line pharmacotherapies for PTSD, there are no specific pharmacotherapy recommendations for sleep problems.²³ In a small study surveying veterans with PTSD, trazodone, a 5-HT₂ antagonist, was associated with decreased nightmare frequency and improvements in sleep onset latency;²⁶ however, randomized controlled trials are needed to determine efficacy.

An updated algorithm by the Psychopharmacology Algorithm Project at the Harvard South Shore Project (PAPHSS) published in 2022 recommends prasozin, an alpha-1 adrenergic receptor antagonist, as a first-line agent for addressing sleep disturbances and nightmares associated with PTSD.²⁷ In deed, prasozin has shown improvements in reducing nightmare frequency in several studies (see Khachatryan et al.²⁸ for a meta-analysis). However, a multisite Veterans Affairs Cooperative randomized controlled trial found no benefit of prasozin in alleviating nightmares or improving sleep quality among veterans with chronic PTSD.²⁹ Like psychological interventions for nightmares, more work is needed to determine which treatment modalities are efficacious for different patient populations.

CONCLUSION

Sleep disturbances are central features of PTSD that contribute to the development and persistence of the disorder. In addition to the insomnia and recurrent nightmares that are embedded within the diagnostic criteria for PTSD, other sleep disorders frequently co-occur that can interfere with successful PTSD treatment and contribute to adverse health outcomes. Interventions for treating sleep problems and PTSD symptoms in trauma-exposed patients are promising, but more work is needed to determine treatment factors for this population, such as modality, sequencing, and adjunctive components.