REM SLEEP AND THE DURATION OF PTSD IN A YOUNG ADULT POPULATION
http://dx.doi.org/10.5665/sleep.3922
A Relationship between REM Sleep Measures and the Duration of
Posttraumatic Stress Disorder in a Young Adult Urban Minority Population
Thomas A. Mellman, MD; Ihori Kobayashi, PhD; Joseph Lavela, BS; Bryonna Wilson, BS; Tyish S. Hall Brown, PhD
Howard University College of Medicine Department of Psychiatry and Behavioral Sciences, Howard University, Washington, DC
Study Objective: To determine relationships of polysomnographic (PSG) measures with posttraumatic stress disorder (PTSD) in a young adult,
urban African American population.
Design: Cross-sectional, clinical and laboratory evaluation.
Setting: Community recruitment, evaluation in the clinical research unit of an urban University hospital.
Participants: Participants (n = 145) were Black, 59.3% female, with a mean age of 23.1 y (SD = 4.8). One hundred twenty-one participants (83.4%)
met criteria for trauma exposure, the most common being nonsexual violence. Thirty-nine participants (26.9%) met full (n = 19) or subthreshold
criteria (n = 20) for current PTSD, 41 (28.3%) had met lifetime PTSD criteria and were recovered, and 65 (45%) were negative for PTSD.
Measurements and Results: Evaluations included the Clinician Administered PTSD Scale (CAPS) and 2 consecutive nights of overnight PSG.
Analysis of variance did not reveal differences in measures of sleep duration and maintenance, percentage of sleep stages, and the latency to and
duration of uninterrupted segments of rapid eye movement (REM) sleep by study group. There were significant relationships between the duration
of PTSD and REM sleep percentage (r = 0.53, P = 0.001), REM segment length (r = 0.43, P = 0.006), and REM sleep latency (r = -0.34, P < 0.03)
among those with current PTSD that persisted when removing cases with, or controlling for, depression.
Conclusions: The findings are consistent with observations in the literature of fragmented and reduced REM sleep with posttraumatic stress
disorder (PTSD) relatively proximate to trauma exposure and nondisrupted or increased REM sleep with chronic PTSD.
Keywords: minority, polysomnography, posttraumatic stress disorder, sleep
Citation: Mellman TA, Kobayashi I, Lavela J, Wilson B, Hall Brown TS. A relationship between REM sleep measures and the duration of
posttraumatic stress disorder in a young adult urban minority population. SLEEP 2014;37(8):1321-1326.
INTRODUCTION
Sleep disturbances, which are denoted by diagnostic criteria
of trauma-related nightmares and difficulty initiating and maintaining sleep, are highly prevalent features of posttraumatic
stress disorder (PTSD)1,2 and have been linked to the development of the disorder.3–5 It is therefore important to understand
the nature of sleep disturbances in PTSD beyond the level of
reported symptoms. Polysomnography (PSG) provides assessment of the timing, duration, and continuity of sleep states
and their associated neurophysiologic activity. There has been
substantial PTSD research using PSG that has lent some clarity
as well as continuing controversy regarding the nature of sleep
disturbances in the disorder. Overall, this body of research
has provided evidence for and against objective impairment
of sleep initiation, maintenance, and depth, and abnormalities
related to rapid eye movement (REM) sleep.
In a meta-analysis of 20 PTSD PSG studies done before
2007, there were no significant effects of PTSD for sleep
latency and efficiency, and wake after sleep onset (WASO);
however, participants with PTSD exhibited lighter sleep (more
stage 1, less stage 3) compared with controls.6 Generalizability
of the meta-analysis is limited by the preponderance of the
A commentary on this article appears in this issue on page 1281.
Submitted for publication November, 2013
Submitted in final revised form January, 2014
Accepted for publication January, 2014
Address correspondence to: Thomas A. Mellman, Howard University College of Medicine, 520 W. St, NW, Washington DC 20059; Tel: 202-8067818; E-mail: [email protected].
SLEEP, Vol. 37, No. 8, 2014
studies (14 of 20) having featured male veteran combat populations, mostly with PTSD durations exceeding a decade. In fact,
two more recent studies that featured predominantly female
samples with non-military trauma did find objective differences
in sleep initiation and/or maintenance; however, variance with
the prior studies also may have been related to recordings done
in home environments.7,8
Interest in possible abnormalities related to REM sleep in
PTSD has been inspired by the occurrence of nightmares that are
distinct from normal dreams in terms of their recurring nature
and, to varying degrees, replicating past (traumatic) experiences.9 Dreams most commonly arise from REM sleep10 and do
not normally represent unaltered memories of specific events.11
In addition, the REM sleep state provides conditions that are
conducive to modification of memory networks, including
their decoupling from affective arousal (which is postulated
to aid emotional adaptation),12 and this process appears to be
impaired in PTSD. A final rationale for examining REM sleep
with PTSD is to determine the overlap or contrast with REM
sleep abnormalities that have been documented for depression,13 a condition that has both common clinical features and
frequent comorbidity with PTSD.14
Studies, including the aforementioned meta-analysis, have
not found consistent reductions in the latency to REM sleep
or increased percentages of REM sleep that characterize
major depression. Kobayashi et al.6 did report increased REM
density (frequency of eye movements within REM periods)
with PTSD. Increased REM density has also been associated
with depression,14 but also with the intensive dreaming15 and
learning periods.16 In a study that uniquely obtained PSG data
within 1 mo of trauma exposure, REM density was increased
with trauma exposure but not with developing PTSD.17 Thus,
1321
REM Sleep and PTSD Duration—Mellman et al.
the pathophysiological significance of REM density in PTSD
remains unclear.
Most nightmares and other symptomatic awakenings in
PTSD have been found to arise from, and thereby disrupt,
REM sleep.18,19 In the study from the early aftermath of trauma,
the lengths of uninterrupted segments of REM sleep (REM
segment length) were shorter among the injured patients developing PTSD.17 An earlier, more anecdotal report observed
“severe deficiency in REM sleep” in association with acute
combat fatigue.20 Findings from some21–23 but not all23–25 of
the studies of established PTSD that have examined relevant
indices are consistent with fragmentation or reduction of REM
sleep. That such patterns have been observed in acute posttraumatic states,17,20 and in patients recruited from acute treatment
episodes with a mean 15 mo duration of PTSD,21 and 2–2.5
y of combat neurosis,”22 whereas no REM sleep disruption25
and increased REM sleep percentage26 have been observed
with combat-related PTSD of approximately 20 y, suggests that
the duration of PTSD may influence patterns of REM sleep.
Considerations of sex effects on relationships between REM
sleep and PTSD were raised in a recent study of Richards et
al.,27 where an increase in REM sleep percentage with PTSD
was seen in females but not in males.
Studies that increase the diversity of populations represented in the sleep PTSD literature and allow for examination
of possible effects of PTSD duration and sex are indicated.
The current study reports data from a nonclinical urban
minority population with high rates of trauma exposure. With
the exception of the study of Breslau et al., in which 59 of the
71 cases of PTSD had remitted,23 such groups are not represented in the sleep PTSD literature. The purpose of this report
is to provide evaluation of relationships of PSG measures and
PTSD that include examination of the duration of the disorder
and participant sex, in a young adult urban African American
population.
METHODS
Participants
The study advertised to recruit young adult (age 18–35 y)
African Americans for a study that examined associations
between trauma, PTSD, sleep, and nocturnal blood pressure. The participants were recruited from the Washington,
DC metropolitan area through study fliers posted in strategic
community settings and through referrals from previous
participants. During the initial screening, potential participants were excluded if they were found to have a body mass
index ≥ 40, chronic medical conditions or psychotic disorders, bipolar disorder, severe recurrent depression, daily use
of any medication, excessive use of caffeine (more than five
cups of coffee per day or its equivalent), heavy smoking
(more than 20 cigarettes per day) and drinking (more than
14 drinks/w in men, more than seven drinks/w in women),
and regular night shift work or unusual sleep-wake schedules. Additional exclusion criteria were sleep, breathing,
and movement disorders (screened through the first night
PSG), current alcohol or drug abuse or dependence (screened
through a structured clinical interview), and positive urine
toxicology for illicit drugs. The study was approved by the
SLEEP, Vol. 37, No. 8, 2014
Howard University Institutional Review Board and all participants signed approved consent forms after they were given
time to review and ask questions.
Measures
Self-Report
The Life Event Checklist (LEC) was administered during
the initial meeting to obtain preliminary information regarding
participants’ trauma exposure. The LEC includes a list of 16
types of potentially traumatic experiences (e.g., transportation accident, assault with a weapon, sexual assault). Participants were asked to indicate whether they had experienced or
witnessed any of these events as an adult or a child and which
of those experiences distressed them the most.28
The Patient Health Questionnaire (PHQ-9) was administered
to obtain a continuous measure of depression severity.29 The
nine question-items are based directly on the diagnostic criteria
for major depressive disorder in the Diagnostic and Statistical
Manual for Mental Disorders, Fourth Edition (DSM-IV) with
response options ranging from “0” (not at all) to “3” (nearly
every day).
Interview
The Clinician Administered PTSD Scale (CAPS),30 a
structured clinical interview, was used to determine lifetime
and current PTSD diagnostic status and symptom severity
according to the diagnostic criteria of the DSM-IV. After the
most distressing potentially traumatic event (the index event)
initially screened by the LEC was confirmed, the event was
further assessed at the beginning of the interview to determine
whether it met the diagnostic criteria for a traumatic event
(Criterion A). If criteria were met, the frequency and intensity of each of 17 PTSD symptoms were rated on five-point
scales ranging from 0 (Never [frequency], Not at all [intensity])
to 4 (Daily or almost daily, Extremely) for both the current
period (past month) and the most symptomatic period of the
participant’s life. To determine diagnostic status, a symptom
was considered present when the participant reported at least
the frequency rating of 1 and the intensity rating of 2 for the
symptom. When a participant met criteria for two of the three
DSM-IV symptom diagnostic clusters, he or she was considered to have a subthreshold PTSD diagnosis. For participants
who had met full disorder criteria in the past but no longer met
full or subthreshold diagnostic criteria, the time frame for when
the PTSD remitted was carefully assessed. PTSD duration was
determined as the number of months from the onset of PTSD
symptoms (during or just following trauma exposure in all but
one case where PTSD related to childhood sexual abuse was
precipitated by early adult experiences) to the time of remission
or the time of the assessment for those who continued to meet
full or subthreshold criteria for PTSD.
Current and lifetime diagnoses of mood disorders, psychotic
disorders, anxiety disorders other than PTSD, substance abuse
and dependence, and eating disorders were assessed using the
Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID).31
All CAPS and SCID interviews were conducted by trained
staff members (psychology graduate students and clinical
1322
REM Sleep and PTSD Duration—Mellman et al.
psychology postdoctoral fellows), and a licensed psychiatrist
(TAM) reviewed all cases. Practice interviews were completed
prior to data collection until the trainee and the trainer reached
the 90% agreement rate on practice cases. For all of the included
participants meeting criteria for current major depression, the
episode was determined to be secondary in temporal onset and
in severity to PTSD.
Screened/self-report
n = 543
Polysomnography
Participants underwent two consecutive overnight PSG
recordings in the Howard University Clinical Research Unit.
None were shift workers or had regular nocturnal activity,
and recordings were scheduled to approximate their natural
bedtimes. Recordings were conducted using an Embla (Denver,
Co) titanium portable unit. PSG collection included a standard
electroencephalogram montage with bilateral frontal, central,
and occipital leads, two electrooculograms (EOG), and chin
electromyogram (EMG) with limb EMGs and respiratory
monitors on the first night only. Scorers were trained by a registered PSG technician. Rules for the onset and termination of
REM sleep and other American Academy of Sleep Medicine
(AASM) criteria32 were emphasized during the training. Records
of novice scorers were also independently scored by experienced scorers, and any discrepancies were addressed. Independent scoring required 90% concordance of epoch scoring
for at least three records. Scorers were blinded to participants’
PTSD status and visually scored sleep records on a computer
monitor and designated the sleep stage of each 30-sec epoch.
After recording time in bed, the REM logic scoring system
(Embla) calculated standard measures including sleep onset
latency, total sleep time, WASO, sleep efficiency, the latency
to REM sleep, and the percentages of total sleep composed of
N1, N2, N3 (slow wave sleep), and REM sleep. Calculation
of REM segment length used our previous criteria17 of at least
two epochs of consecutive REM sleep with no more than one,
30-sec epoch of non-REM sleep interruption. Eye movements
during REM sleep were also scored based on previously used
criteria of EOG lead excursions of at least 25 µV within 500
milliseconds.17 REM density was calculated by dividing the
number of eye movements (EMs) by minutes of REM sleep.
Data Analysis
Demographic data and clinical and sleep measures were
compared between participants based on PTSD status by
one-way analysis of variance (ANOVA) and possible differences between the study groups with current full PTSD, current
subthreshold PTSD, lifetime PTSD, and PTSD negative with
trauma exposure and PTSD negative without trauma exposure were explored by independent t-tests. We then examined
Pearson correlations between PTSD severity and duration and
the sleep measures. The square root transformation of PTSD
duration was used to correct for the skewed distribution of the
variable. To exclude potentially confounding roles of remission
and depression on relationships between the sleep measures of
interest, we also conducted analyses of just those with current
(full and subthreshold) PTSD with and without those with
concurrent criteria for major depression, as well as regression
analyses that included depression severity as measured by the
Patient Health Questionnaire (PHQ-9) as a covariate.
SLEEP, Vol. 37, No. 8, 2014
Invited for interview/lab
n = 177
Excluded:
• Tox screen + (n = 15)
• Apnea (n = 6)
• Other protocol violations or
technical problems (n = 11)
Final sample
n = 145
Figure 1—Study enrollment.
RESULTS
Participants
Of the 177 participants invited to the laboratory phase of the
study, 15 were excluded for positive urine screenings for illicit
drugs. An additional six participants (one with current PTSD,
five negative for PTSD) were found to have apnea/hypopnea
indices exceeding 10 events/h on the first night PSG. An additional 11 were not included because of loss to follow-up or poor
quality recordings (Figure 1). The demographic, clinical and
sleep measures for the remaining 145 participants are presented
in Table 1. All of the final sample participants were Black with
123 self-identifying as African American, 11 African, 11 Caribbean, and 86 (59.3%) were female. Their mean age was 23.1
(standard deviation [SD] = 4.8). There were 121 participants
(83.4%) who were determined by the CAPS to have experienced a criterion A trauma. The most common categories of
index traumas were physical abuse and assault for 23.1% of the
total participants and sexual trauma for 18.8% (27.8% of the
females). Other categories for index traumas included witnessing
community violence (13.4%), sudden unexpected deaths
(12.2%), transportation accidents (7.3%), disasters (6.9%), and
other (1.7%). Nineteen participants met full current criteria for
PTSD, 20 met current subthreshold criteria (10 of whom met
full PTSD criteria in the past), totaling 39 participants or 26.9%
of the group with current PTSD. Forty-one participants (28.3%)
had met lifetime criteria and were recovered and 65 (44.8%),
including 24 who were not trauma exposed, had never met
criteria for PTSD (PTSD negative). There were no significant
differences in age between these major groupings. There was a
trend toward different sex distributions, with 64% of those in
the current PTSD group, 71% of those from the lifetime (recovered) group, and 49% of the PTSD negative group being female
(chi square = 5.3, df = 2, P < 0.07). As expected, CAPS scores
were highest for those with current PTSD (41.9, SD = 17.7)
followed by the lifetime recovered group (12.9, SD = 8.6) and
the PTSD negative group (6.6, SD = 7.5) [F(2,118) = 97.3,
118; P < 0.001]. For the current PTSD and lifetime recovered
groups, the mean duration of PTSD was 35.6 mo (SD = 51.3)
and for the current PTSD group alone, 64.1 mo (SD = 62.9)
1323
REM Sleep and PTSD Duration—Mellman et al.
Table 1—Sleep measures by groups defined by posttraumatic stress disorder and trauma
Female, n (%)
Age
CAPS score (n = 120)
Duration (mo) PTSD (n = 80)1
Total sleep (min)
Latency (min)
WASO (min)
Sleep efficiency (% TIB spent asleep)
N1 (% TST)
N2 (% TST)
N3 (% TST)
REM sleep (% TST)
REM latency (min)
REM segment length (min)
REM density (mean eye movements/
min REM sleep)
Total (n = 145)
86 (59.3%)
23.1 (4.8)
20.1(19.4)
35.6 (51.3)
385.3 (73.4)
34.1 (44.3)
26.3 (25.4)
86.5 (10.2)
2.5 (1.7)
51.9 (7.7)
24.6 (9.2)
21.1 (6.0)
79.1(34.9)
15.5 (5.9)
2.4 (2.3)
Current
(subthreshold)
PTSD (n = 20)
11 (55%)
21.7 (3.8)
29.3 (7.3)
47.2 (47.9)
377.5 (60.4)
42.9 (52.0)
25.4 (15.3)
85.5 (10.8)
2.4 (1.0)
51.8 (8.2)
26.2 (9.0)
19.8 (6.2)
84.1 (34.0)
16.1 (5.9)
2.3 (1.5)
Current (full)
PTSD (n = 19)
14 (64.1%)
22.4 (4.7)
41.9 (17.7)
75.4 (72.6)
385.2 (73.4)
23.4 (32.5)
36.2 (37.7)
87.5 (10.2)
2.2 (1.2)
51.3 (9.4)
25.3 (10.9)
21.1 (6.0)
89.2 (48.6)
16.1 (6.1)
1.7 (1.3)
Lifetime
(recovered)
PTSD (n = 41)
29 (70.7%)
24.3 (5.1)
12.9 (8.6)
11.0 (13.9)
388.1 (70.5)
34.6 (41.3)
20.5 (13.9)
86.5 (11.6)
2.3 (1.8)
53.0 (6.0)
24.0 (7.7)
20.9 (6.2)
80.3 (30.4)
14.5 (5.6)
2.3 (2.0)
Trauma
No PTSD
(n = 41)
21 (49.2%)
22.9 (4.6)
6.6 (7.5)
NA
368.4 (77.5) a
35.5 (54.3)
26.8 (31.9)
86.3 (11.1)
2.5 (2.0)
49.9 (7.9) a
25.0 (10.0)
22.6 (5.6)
74.6 (35.8)
16.9 (6.3)
2.9 (2.8)
Trauma
Negative
(n = 24)
11 (45.8%)
23.7 (5.8)
NA
NA
416.3 (76.1) a
31.9 (31.1)
28.2 (22.0)
87.0 (8.4)
2.4 (2.0)
54.3 (7.7) a
23.1(9.4)
20.0 (5.8)
73.1 (28.1)
14.1 (5.4)
2.4 (2.7)
P < 0.05 by exploratory t-tests. Values reported are mean (standard deviation) unless indicated otherwise. CAPS, Clinician Administered PTSD Scale;
PTSD, posttraumatic stress disorder; REM, rapid eye movement; WASO, wake after sleep onset.
a
(see Table 1 for subgroup means). Durations were significantly
greater for those with current full [t(58) = 3.84; P = 0.001] and
subthreshold PTSD [t (59) = 3.24, P = 0.004] compared with
those in the lifetime recovered group.
but not REM segment length remained when the eight participants with current major depression were excluded from the
analysis (see Table 2). In regression analyses, however, REM
segment length (beta = 0.30, t = 2.61, P < 0.01) (as well as
WASO) were significantly associated with PTSD duration
with depression severity measured by the PHQ-9 included in
the model (see Table 3). Inverse correlations of REM latency
with PTSD severity (measured by the CAPS) in the current
PTSD group were close to meeting the threshold for statistical
significance (r = 0.31, P = 0.06 with major depressive episode,
MDE included; r = 0.33, P = 0.07 with MDE excluded) (see
Table 2).
Sleep Measures by Groups
There was no effect of combining individuals with full
versus subthreshold current PTSD in the current PTSD group or
trauma exposed versus unexposed in the PTSD negative group
and on the findings of no significant differences between groups
by one-way ANOVA. The t-tests exploring possible differences
between the subgroups were significant without correction for
multiple comparisons only for trauma exposed versus trauma
unexposed PTSD negatives for total sleep time [368.4 ± 77.5
versus 416.3 ± 76.1; t(63) = 2.42, P = 0.02] and percentage of
N2 sleep [49.9 ± 7.9 versus 54.3 ± 7.7; t (63) = 2.15, P = 0.04]
(see Table 1). REM density was the only sleep measure that
differed between males and females [2.9 EMs per min of REM
sleep for females, SD = 2.59 versus 1.8 for males, SD = 1.47;
t(143) = 2.95; P < 0.004].
Sleep Measures and PTSD Severity and Duration
Pearson correlations were significant for the (square root
transformed) duration of PTSD and WASO (r = 0.32, P = 0.004)
as well as the percentage (r = 0.25, P = 0.03) and segment
length (r = 0.30, P = 0.007) of REM sleep in the combined
current PTSD and lifetime groups (n = 80). Relationships
with REM percentage (r = 0.53, P = 0.001), and REM segment
length (r = 0.43, P = 0.006) but not WASO remained significant and also included a negative association of PTSD duration and REM sleep latency (r = -0.34, P = 0.03) within the
current PTSD group (n = 39). The strength and significance
of the associations with REM latency and REM percentage
SLEEP, Vol. 37, No. 8, 2014
DISCUSSION
The current study contributes new findings from a no-clinical population with limited representation in the sleep/PTSD
literature, specifically, a minority group with high rates of exposure to traumas that most commonly relate to urban violence.
Our study population is among the largest for the sleep PTSD
literature and features comparable numbers of male and female
participants with varying and well-characterized degrees and
duration of PTSD. Other than a possible reduction in sleep
time associated with trauma exposure, analyses did not detect
group differences based on PTSD or trauma exposure status.
None of the PSG findings reported in the sleep PTSD literature
including reduced slow wave sleep,6,27 impaired sleep maintenance,7,8,18 elevated REM density,6 and patterns of fragmented
REM sleep17,21–23 have been consistently found across all studies.
The absence of differences by PTSD categories here could be
related to the relatively low PTSD severity in our nontreatmentseeking study group, as well as the degree to which sleep was
compromised in the overall study population of young adult
minorities living in stressful urban environments (e.g. mean
1324
REM Sleep and PTSD Duration—Mellman et al.
Table 2—Relationships of wake after sleep onset and rapid eye movement measures to posttraumatic stress disorder severity and duration (Pearson
correlations).
All trauma exposed participants
(n = 121)
CAPS
0.10
0.16
-0.05
0.01
WASO
REM latency
REM percentage
Ave. REM segment length
Current PTSD
(n = 39)
PTSD Duration a
(n = 80 b)
0.32 d
-0.17
0.25 c
0.30 d
CAPS
0.18
0.31
0.03
0.08
Current PTSD no MDE
(n = 31)
PTSD Duration
0.25
-0.34 c
0.53 d
0.43 d
CAPS
0.27
0.33
-0.16
-0.05
PTSD Duration
0.04
-0.45 c
0.48 d
0.29
Square root transformed. b 80 participants with current full or subthreshold PTSD or lifetime recovered PTSD. c P < 0.05. d P < 0.01. CAPS, Clinician
Administered PTSD Scale; PTSD, posttraumatic stress disorder; REM, rapid eye movement; WASO, wake after sleep onset.
a
Table 3—Regressions – posttraumatic stress disorder duration and depression severity (Patient Health Questionnaire) on wake after sleep onset and rapid
eye movement sleep measures
WASO
PTSD duration a
PHQ-9
a
Beta
0.24
0.14
t
2.35
1.19
REM latency
Sig.
0.04
0.24
Beta
-0.15
0.05
t
-1.19
0.41
REM percentage
Sig.
0.24
0.68
Beta
0.19
0.17
t
1.56
1.42
Sig.
0.12
0.16
REM segment
Beta
0.30
0.21
t
2.61
1.89
Sig.
0.01
0.06
Square root transformed. PHQ-9, Patient Health Questionnaire; PTSD, posttraumatic stress disorder; REM, rapid eye movement; WASO, wake after sleep onset.
6.4 h of total sleep, mean of 26 min of wake after falling asleep
prior to the terminal awakening).
As reviewed in the Introduction, the prior studies that have
varied with regard to the amount and continuity of REM sleep
feature a wide range of PTSD durations. Our analyses revealed
significant positive relationships of REM sleep segment length
and the percentage of REM sleep with the number of months
participants had or continued to have PTSD symptoms. These
correlations were strengthened and included a negative association with REM sleep latency, when only those with current PTSD
were analyzed. The correlations between REM sleep percentage
and REM sleep latency with PTSD duration remained significant
after removing participants with major depression, and for REM
segment length, when controlling for depression severity. Thus,
our findings are consistent with prior literature where reduction
or fragmentation of REM sleep has been observed in the acute
aftermath of trauma exposure,17,20 and in acutely symptomatic
populations within several years of the onset of PTSD,21,22 and
the observations of undisrupted or increased REM sleep made
in veterans approximately 20 y after combat exposure.25,26 Our
new findings and those from the literature are consistent with
processes where reactions to trauma among those in whom
PTSD develops are suppressive or disruptive to REM sleep,
whereas secondary processes over time promote REM sleep.
Acute suppressive and disruptive effects of trauma exposure on
REM sleep are consistent with a model of fear conditioning in
stress sensitive rodents.33 That REM sleep would recover over
time is consistent with observations of “rebound” that occurs
following experimental REM sleep deprivation or withdrawal
of REM suppressive pharmacological agents or substances.34
Adaptations of brainstem adrenergic receptors to overstimulation could be a mechanism that underlies recovery of REM
SLEEP, Vol. 37, No. 8, 2014
sleep over the course of PTSD. Models of sleep state regulation posit that noradrenergic (NA) deactivation is permissive to
REM sleep onset, and NA stimulation is critical to terminating
the REM state.35 Increased NA activity and/or sensitivity has
been implicated in the general pathophysiology of PTSD36
and in hyperarousal during sleep.37,38 Theories that REM sleep
can serve an adaptive role in processing trauma memories12,17
would posit that increases in REM sleep duration and consolidation over time could aid PTSD recovery. Conversely, given
high rates of comorbid depression with chronic PTSD14 and the
association of depression with indices of increased pressure for
REM sleep,13 increasing REM sleep activity could be indicative
of biological processes common to the progression of PTSD and
major depression. Our observations were not accounted for by
co-occurring major depression, however, and were from a population that was largely functioning despite their PTSD symptoms.
Other findings of note include an exploratory observation
of a possible effect of trauma on sleep duration, and between
the duration of PTSD and sleep disruption as indicated by
WASO. There are bidirectional possibilities for explaining the
latter relationship, where impaired sleep maintenance could
impede PTSD recovery and/or persisting PTSD could promote
disrupted sleep. It is of note that the significant correlative relationships were with PTSD duration and with the exception of
a relationship between REM sleep latency that was close to
significance (P < 0.06), not with PTSD severity. It is possible
that a study population with more severe PTSD represented
would have exhibited such relationships.
Possible inaccuracies of reporting times of PTSD onset and
remission are also limitations of our study. Prospective longitudinal data under naturalistic and/or treatment conditions
would more definitively elucidate the nature and significance of
1325
REM Sleep and PTSD Duration—Mellman et al.
relationships between REM sleep measures and the course of
PTSD. In addition to being cross-sectional, other limitations of
our study include the use of participants with full and subthreshold
diagnoses and reliance on a single night recording (obtained after
an adaptation night) from the setting of a clinical research unit.
The findings do suggest that there are time-dependent relationships of PTSD and sleep, particularly REM sleep, which
likely have implications for the persistence or recovery of the
disorder. We hope future investigations will examine these relationships prospectively while probing their underlying mechanisms and effect on outcomes.
ACKNOWLEDGMENTS
The authors acknowledge the contributions of Duaa Altee
and Latesha McLaughlin for recruiting and evaluating participants and managing data, and Enkutash Alemeyhu, Edward
Huntley, and Nancy Cowdin for scoring PSG records, all of
whom were compensated.
DISCLOSURE STATEMENT
This was not an industry supported study. This research
was supported by a National Heart, Lung, and Blood Institute
grant R01HL087995 to Dr Mellman and a National Center for
Advancing Translational Sciences grant UL1RR031975 for
the Georgetown-Howard Universities Center for Clinical and
Translational Science. The study was conducted at the Howard
University Clinical Research Unit. The authors have indicated
no financial conflicts of interest.
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