Do weighted blankets improve sleep among children with a history of maltreatment? A randomized controlled crossover trial

Abstract

Study Objectives:

Sleep disruption is prevalent and persistent among children who experience maltreatment/interpersonal trauma. Weighted blankets have gained popularity in recent years as a potential nonpharmacological intervention for improving sleep in various populations, but their efficacy has not been examined among maltreated children. The current study used a randomized, within-subjects, crossover design to examine whether the use of a weighted blanket improves objective and/or subjective indices of sleep among 30 children, ages 6–15 years (mean = 9.7, standard deviation = 2.9) adopted from foster care.

Methods:

Participants used a weighted blanket for 2 weeks and their usual (unweighted) blanket for 2 weeks in a counterbalanced order. Sleep outcomes were measured using actigraphy and subjective sleep diaries.

Results:

No differences in actigraphy-based or subjective estimates of total sleep time, sleep onset latency, wake after sleep onset, or sleep quality ratings were found based on blanket type. Child age, biological sex, timing of participation (school year vs summer months), and maltreatment/trauma history did not impact outcomes.

Conclusions:

Although we did not find evidence that weighted blankets improve sleep among children with a history of maltreatment/interpersonal trauma, additional well-controlled studies using larger samples of children are needed.

Citation:

Cifre AB, Vieira A, Baker C, et al. Do weighted blankets improve sleep among children with a history of maltreatment? A randomized controlled crossover trial. J Clin Sleep Med. 2024;20(9):1405–1413.

BRIEF SUMMARY

Current Knowledge/Study Rationale: Sleep disruption is common among children with a history of maltreatment, but controlled studies investigating efficacious sleep interventions for this population are lacking. Anecdotal reports suggest weighted blankets might help improve sleep among maltreated children.

Study Impact: To our knowledge, use of weighted blankets for improving sleep has not been examined among youth with a history of maltreatment despite compelling reasons for such work. Findings underscore the importance of using rigorous methods that control for potential placebo effects as well as a need for more research.

INTRODUCTION

Healthy sleep is essential for children’s physical, cognitive, and emotional development, and plays a critical role in overall well-being across the lifespan.¹ Children who experience persistently poor sleep are at an elevated risk for a wide range of negative outcomes, including academic difficulties, behavioral problems, obesity, and psychiatric disorders.^2,3 While many youth experience periodic sleep difficulties, children who experience maltreatment and other forms of interpersonal trauma (eg, exposure to domestic violence) display elevated rates of both acute and long-term sleep disturbances.^4–7 For example, a large proportion of children in foster care (ie, due to abuse and/or neglect) have problems falling asleep, nighttime awakenings, nightmares, and/or parasomnias.^8–11 Even after adoption (ie, permanence), a large proportion of children previously placed in foster care struggle with sleep.^12–14 Using actigraphy, Glod et al¹⁵ found abused children to exhibit significantly greater motor activity during sleep compared to both depressed and control children. Sleep problems among maltreated children are in turn predictive of greater emotional and behavioral difficulties.^13,16 Unfortunately, controlled studies examining the efficacy of sleep interventions for children who experience maltreatment and other types of interpersonal traumas are generally absent from the literature.

In recent years, weighted blankets (WBs) have gained popularity as a nonpharmacological intervention for improving sleep quality and/or reducing anxiety across both healthy and clinical populations of children and adults.¹⁷ Positive outcomes attributed to the use of WBs are theorized to emerge via sensory effects of deep pressure stimulation. More specifically, deep pressure stimulation via the use of weighted items (eg, blankets, vests) is thought to produce feelings of relaxation and a sense of calm through the activation of the parasympathetic nervous system.^18,19 Empirical support for this hypothesis is limited, although use of a WB has been shown to lower electrodermal activity,¹⁹ a proxy of sympathetic nervous system activity. Another recent study among healthy adults found that use of a WB was associated with greater increases of melatonin in the hour before sleep compared to a light blanket, although differences in sleep variables were not observed.²⁰ It is also speculated that deep pressure stimulation may improve sleep and reduce anxious feelings via greater release of serotonin (a neurotransmitter involved in regulating sleep and mood), reduction of the stress hormone cortisol, and/or activation of the oxytocinergic system.^17,19,20 Psychologically, a WB might mimic the effects of a warm hug/embrace, promoting feelings of calm and security.^17,19

Despite the availability of numerous anecdotal and qualitative reports in the literature, controlled trials of WB use during sleep are highly limited. Available studies in child samples mainly include youth with autism spectrum disorders and/or attention-deficit/hyperactivity disorder (ADHD)^17,21–23 and have produced mixed results. In one of the largest randomized, controlled crossover studies, including 5- to 16-year-old children with autism spectrum disorder, use of a WB compared to a control blanket did not result in objective or subjective improvements in total sleep time (TST), sleep onset latency (SOL), or other sleep parameters, even though both parents and children reported a preference for the WBs.²² Among 8- to 13-year-olds with ADHD, 2 smaller studies using actigraphy and sleep diaries have found reduced SOL (as well as improvements in daytime activity levels and attention) following use of a WB at night;^24,25 however, neither study included a comparison control condition. A more recent randomized control trial among 6–14 year-old youth with ADHD found improvements in actigraphy-measured TST, wake minutes after sleep onset (WASO), and sleep efficiency compared to a control group.²³ Qualitative reports from parents of children with ADHD have also indicated perceived improvements in children’s sleep when using a WB.²⁶ It is possible that the mechanisms through which WBs improve sleep might differ among different child populations. For example, for youth with ADHD, who have a high incidence of periodic limb movements during sleep,²⁷ WBs may serve to lessen sleep-disruptive movements and improve overall sleep quality.²⁸

To our knowledge, use of WBs for improving sleep has not been examined among youth with a history of maltreatment despite compelling reasons for such work. Self-regulatory deficits, including regulation of arousal states, are common among maltreated youth²⁹ and thought to emerge from overactivation of stress response systems including the hypothalamic-pituitary-adrenal axis. Since regulation of biological responses to stress and maintaining circadian rhythms of hormone production (eg, cortisol and melatonin) are essential functions of the hypothalamic-pituitary-adrenal system,³⁰ bidirectional relationships with sleep exist. Thus, just as chronic exposure to stress and/or trauma contributes to sleep disruption, sleep that is inadequate or fragmented creates a feedback loop through which anxiety and hyperarousal are maintained.^31,32 Accordingly, hyperarousal is one pathway through which adversity is theorized to give rise to insomnia and other forms of sleep-wake dysregulation.^33,34 Based on the theory that deep pressure stimulation induces feelings of relaxation and calm via 1 or more neurophysiological systems, WBs may be particularly helpful for youth with a history of maltreatment.

Additionally, the unique experiences of maltreated children, which may include harsh, unpredictable, or nonresponsive caregivers and attachment disruptions, among others, are likely to diminish feelings of security and safety essential for restful sleep.^35,36 At a neurobiological level, childhood maltreatment produces alterations in both brain structure and function that affect sensory processing and modulation.³⁷ Because touch is an important sensory channel through which children develop a sense of safety and self-regulatory skills,³⁸ and nurturing tactile interactions in childhood are linked with more adaptive physiological, social, and emotional functioning,^39–41 sensory-based interventions are increasingly endorsed for maltreated youth. In fact, van der Kolk⁴² posits that interventions for maltreated children need to focus on sensory input as much as or more so than cognitive processes to be optimally effective in reducing behavioral and emotional difficulties. Positive sensory effects may partly explain anecdotal parent reports of improved sleep among maltreated youth who use WBs,^43,44 but controlled studies are needed.

Present study

In view of the adverse early experiences of children who spend time in foster care, as well as high rates of sleep disruption in this population that persist even after achieving permanency, WBs may offer a convenient, nonpharmacological treatment option for improving sleep health. We therefore compared the use of a WB to children’s usual blanket on several sleep outcomes among youth, ages 6–15 years, adopted from foster care. In an exploratory randomized crossover trial, youth used their usual (unweighted) blanket and a WB each for a period of 2 weeks, during which sleep was monitored continuously with daily diaries and actigraphy. Based on available anecdotal reports, we hypothesized that use of a WB would result in better objective sleep (ie, longer sleep duration, shorter SOL, and less WASO) compared to children’s usual (unweighted) blanket. Based on subjective sleep diary data, we hypothesized that use of a WB would result in longer sleep duration, shorter SOL, and child reports of better sleep quality in the morning compared to children’s usual blanket.

METHODS

Participants

The sample included 30 children and adolescents 6–15 years of age (mean = 9.7, standard deviation = 2.9) adopted from foster care. A total of 37 youth were enrolled in the study; however, 5 families dropped out due to scheduling problems, 1 dropped out due to illness, and 1 was removed from the study due to nonadherence with study procedures. Families were recruited from a large, metropolitan area in the United States through private social media groups on Facebook for adoptive and foster families, and through local foster care and adoption agencies. Youth were eligible if they had been adopted from foster/kinship care, were between the ages of 6 and 15 years, weighed between 50 and 110 pounds (to ensure WBs matched approximately 10% of body weight, similar to prior studies), and scored in the clinical range on a parent-report measure of child sleep problems. Exclusion criteria included: (1) current or previous use of a WB, (2) serious medical conditions requiring routine care and/or use of medical equipment, (3) neurodevelopmental disorder or intellectual disability limiting ability to understand study procedures, (4) confirmed or suspected diagnosis of sleep apnea or other organic sleep disorders, (5) lack of fluency in English (child or caregiver), and (6) current suicidal thoughts and/or behaviors. Eligibility was assessed during an initial phone screen and later confirmed during a comprehensive in-person assessment.

Study design and procedures

During an initial in-person appointment, all study procedures were explained, informed consent/assent was obtained, inclusion/exclusion criteria were confirmed, and youth and parents completed a brief interview and several questionnaires. Children completed clinical measures with the assistance of a research assistant where they were given the option to take breaks or skip questions if they showed signs of distress. Children and parents were told that the purpose of the study was to understand more about the types of blankets children prefer to sleep with to minimize demand characteristics. Participants were weighed at the initial assessment using the same calibrated scale to provide a WB that represented approximately 10% of their body weight. Using a randomized, crossover design, youth were then assigned to 1 of 2 groups: use of a WB for 2 weeks (14 nights) followed by use of their usual (unweighted) blanket (UB) for 2 weeks (WB/UB group), or use of these blankets in the reverse order (UB/WB group). All youth wore wrist actigraphs and completed sleep diaries for the duration of the study. Actigraphy and sleep diary data from the first 3 nights in each blanket condition were not included in analyses to allow children time to adjust to wearing the actigraph and/or using a WB.

Participants assigned to the WB/UB group were given a WB at the initial assessment and participants assigned to the UB/WB group were given a WB at a midstudy assessment, 2 weeks later. The midstudy assessment included the completion of several questionnaires similar to the initial assessment. For youth assigned to the WB/UB group, study staff collected the WB from the family at the midstudy assessment to ensure it was not used during the usual blanket phase of the study. A final poststudy assessment took place 2 weeks later including a similar battery of questionnaires as the initial and midstudy assessments. At the end of the study, youth were given their WB to keep, and parents were given a $15 gift card for their participation. WBs were provided by Luna Blankets (www.lunablanket.com). These cotton blankets use microscopic glass beads woven into the blanket fibers to reduce shifting and allowing for even distribution of weight. This study was approved by the University of Houston Institutional Review Board.

Measures

Demographic characteristics and child history

At the initial assessment, parents answered a series of demographic questions about themselves and their child including information about age, biological sex, gender identity, race/ethnicity, marital status, level of education, and household income. Parents provided information about the child’s history in foster care including the age at which the child was first placed in state custody, number of prior foster placements, and age when their adoption was finalized. Other questions were related to child medical conditions, psychiatric diagnoses, and prescribed and over-the-counter medications.

Sleep assessments

Actigraphy:

Children wore the same wrist actigraph (ActiWatch Spectrum Plus, Philips Respironics) throughout the study. Youth were instructed to press a button on the side of the watch when they got into bed at night and out of bed in the morning to assess SOL and to elucidate timings of nighttime awakenings. After downloading the data, a validated computerized scoring Sadeh algorithm was used to detect sleep and wake periods.⁴⁵ These sleep periods were confirmed against sleep diaries by study staff. Other variables derived from actigraphy for the current study included TST and WASO. All actigraphy variables were averaged during each blanket condition.

Sleep diaries:

Subjective sleep diaries were collected in tandem with actigraphy. Diaries were completed by the child with parental assistance. Diaries included questions about bedtime/waketime, SOL, nighttime awakenings, and how the child felt when waking in the morning (a proxy for subjective sleep quality) measured on a 3-point Likert-type scale. Mean imputation was used to substitute any missing values for SOL in the sleep diaries. TST was determined by calculating total hours from the reported bed to wake time minus SOL.

Sleep questionnaire:

Parent report of children’s sleep was assessed via the Child Sleep Habits Questionnaire⁴⁶ at all 3 assessment points. This 33-item measure assesses sleep during the past week, yielding a total sleep problem score as well as 8 subscale scores: (1) Bedtime Resistance, (2) Sleep Onset Delay, (3) Sleep Duration, (4) Sleep Anxiety, (5) Night Wakening, (6) Parasomnias, (7) Sleep-Disordered Breathing, and (8) Daytime Sleepiness. Responses are recorded on a 3-point Likert scale ranging from “Never” to “Always.” Total Child Sleep Habits Questionnaire scores showed good reliability in the current sample (α = .86).

Clinical measures

Maltreatment/trauma history:

The Child and Adolescent Trauma Screen (CATS)⁴⁷ was completed by youth at the initial assessment. The measure is split into 2 parts. The first includes 15 traumatic events/experiences that may have happened to the child. For any items endorsed as “yes,” children are then asked to indicate if the experience is bothering them at present. Next, the presence of symptoms based on post-traumatic stress disorder criteria are assessed (ie, re-experiencing, avoidance, negative mood/cognitions, and arousal symptoms). Youth indicate how often they were bothered by each symptom over the past 2 weeks on a 4-point Likert scale: 0 “Never,” 1 “Once in a while,” 2 “Half the time,” 3 “Almost always.”

Analytic plan

Since the effects of one condition may “carry over” and alter responses to the subsequent condition in a crossover trial, main analyses were examined for potential blanket effects, period effects, and blanket–period interactions. Blanket effects (ie, treatment effects) were tested with 1-sample t tests comparing within-subject differences when using the WB vs UB. Period effects were tested with 2-sample t tests comparing differences between the conditions (blanket #1 – blanket #2) in the UB/WB and WB/UB groups. Blanket × period interactions were examined with 2-sample t tests comparing the average response of the 2 blankets between the 2 randomized groups (ie, is the difference between the 2 blankets different in the 2 time periods?).

Due to the relatively small sample size, effects sizes were examined in addition to P values. All medium and large effects were explored with post hoc tests even in the absence of statistical significance to explore potentially meaningful relationships for investigation in future studies. Also, given the preliminary nature of our study, the role of child age, biological sex, and timing of participation (school year vs summer/school break) were explored in post hoc analyses (rather than as covariates) using t tests or Wilcoxon signed-rank tests.

RESULTS

Sample characteristics

Child and parent characteristics are summarized in Table 1. The mean age of children was 9.7 years (standard deviation = 2.1), with 19 (63%) females. The sample was relatively diverse with 30% Black and 43% Hispanic children. The average time since the child’s adoption was 6.76 (standard deviation = 3.49) years. Mean total sleep problems score on the Child Sleep Habits Questionnaire was 49 (standard deviation = 9.38) which is above the cut-off for clinically significant sleep disturbance.⁴⁶ Of the total sample, 22 (73.3%) children were reported by parents to have been diagnosed with at least 1 psychiatric disorder, including anxiety disorders, post-traumatic stress disorder, depression, ADHD, bipolar disorder, oppositional defiant disorder, and/or reactive attachment disorder. Also, 19 (63.3%) children were taking at least 1 prescription medication, and 3 (10%) were taking melatonin. We did not control for melatonin use in primary analyses because we used a within-subjects design, all youth scored in the clinical range on a parent-report measure of child sleep problems, and melatonin use was not meaningfully associated with any objective sleep variables at the baseline assessment.

Table 1.

Demographic and clinical variables of the full sample and both groups.

	Total Sample (n = 30)	UB/WB (n = 13)	WB/UB (n = 17)
Child Demographics
Age in years: mean (SD)	9.7 (2.9)	10.4 (3.3)	9.2 (2.6)
Female: n (%)	19 (63.3)	9 (69.4)	10 (58.8)
Hispanic/Latino ethnicity: n (%)	13 (43.3)	5 (38.5)	8 (47.1)
Race: n (%)
White	9 (30.0)	2 (15.4)	7 (41.2)
Black	9 (30.0)	7 (53.8)	2 (11.8)
Native Hawaiian/Pacific Islander	1 (3.3)	1 (7.7)	0 (0.0)
Multiracial	1 (3.3)	0 (0.0)	1 (5.9)
Did not identify a race but did select being Hispanic	10 (33.3)	3 (23.1)	7 (41.2)
CATS score: mean (SD)	3.5 (3.8)	2.7 (3.1)	4.6 (4.8)
CSHQ score: mean (SD)	49.2 (8.9)	50.7 (12.4)	48.2 (5.5)
Parent Demographics
Age in years: mean (SD)	44.1 (7.9)	45.5 (9.1)	43.1 (7.0)
Female: n (%)	28 (93.3)	12 (92.3)	16 (94.1)
Hispanic/Latino ethnicity: n (%)	3 (10.0)	2 (15.4)	1 (5.9)
Race: n (%)
White	20 (66.7)	6 (46.2)	14 (82.4)
Black	8 (26.7)	6 (46.2)	2 (11.8)
Did not identify a race but did select being Hispanic	2 (6.7)	1 (7.7)	1 (5.9)
Yearly household income: n (%)
$10,001–$25,000	1 (3.3)	1 (7.7)	0 (0.0)
$25,001–$50,000	2 (6.7)	1 (7.7)	1 (5.9)
$50,001–$75,000	1 (3.3)	1 (7.7)	0 (0.0)
$75,001–$100,000	6 (20.0)	3 (23.1)	3 (17.6)
$100,001–$150,000	11 (36.7)	3 (23.1)	8 (47.1)
More than $150,001	7 (23.3)	2 (15.4)	5 (29.4)
Prefer not to answer	2 (6.7)	2 (15.4)	0 (0.0)

CATS = Child and Adolescent Trauma Screen, CSHQ = Child Sleep Habits Questionnaire, SD = standard deviation, UB = usual (unweighted) blanket, WB = weighted blanket.

Preliminary analyses

The dataset was first assessed for nonvalid or missing data. Sleep diary data for 2 participants were not included in analyses due to evidence of nonvalid reporting. Actigraphy data were missing for 1 participant due to watch malfunction. Data for any nights that fell the day before, on, or immediately after a national holiday were also excluded from analysis. Similarly, nights when the child was sick, traveling, or had a marked deviation in their schedule were also excluded. Bivariate correlations among all actigraphy and sleep diary variables were examined and are presented in Table 2.

Table 2.

Means, standard deviations, and correlations for sleep variables.

Variable	M	SD	1	2	3	4	5	6	7	8	9	10	11
1. Act TST WB	485.4	54.5
2. Act TST UB	484.4	60.5	.67**
3. Act SOL WB	12.9	11.1	−.34	−.07
4. Act SOL UB	12.9	11.5	−.16	.12	.52**
5. Act WASO WB	46.5	14.2	−.09	−.08	−.13	−.14
6. Act WASO UB	46.3	16.3	−.23	.10	.16	−.02	.72**
7. Subj TST WB	581.4	58.6	.58**	.85**	−.05	.08	.29	.49*
8. Subj TST UB	577.0	69.3	.48*	.86**	.04	.19	.23	.46*	.90**
9. Subj SOL WB	13.2	11.1	−.34	.11	.50*	.37	.00	.31	.01	.10
10. Subj SOL UB	12.6	9.6	−.21	.05	.03	.05	−.12	.03	−.11	−.14	.60**
11. Subj SQ WB	2.5	0.5	.17	.09	−.47*	−.42*	.35	.25	.17	.14	−.39*	.08
12. Subj SQ UB	2.3	0.5	.06	.15	−.23	−.14	.38	.43*	.30	.25	.16	.06	.46*

*P < .05, **P < .01, ***P < .001. Act = actigraphy, Subj = subjective sleep diary, SOL = sleep onset latency in minutes, SD = standard deviation, SQ = sleep quality, TST = total sleep time in minutes, UB = usual (unweighted) blanket, WASO = wake minutes after sleep onset, WB = weighted blanket.

Actigraphy-based sleep outcomes

We examined 3 sleep parameters based on actigraphy: TST, SOL, and WASO; see Table 3. The within-subject mean difference in TST between the blanket types was approximately 1 minute longer during use of the WB compared to the UB; a nonstatistically significant difference based on a small effect, t(27) = 0.10, P = .91, d = 0.02. The period effect was also nonsignificant and small, t(53.611) = 0.26, P = .79, d = 0.07. The blanket × period interaction was nonsignificant and medium in size, t(26) = 1.57, P = .12, d = 0.60. To explore this interaction, we analyzed the mean difference between WB and UB participants during Period 1. The difference was nonstatistically significant and small in size, t(16.17) = 0.50, P = .63, d = 0.21.

Table 3.

Crossover comparisons of WBs in children with a history of maltreatment.

Outcomes	WB-UB (Mean Diff.)	Treat. Effect (t/P Value)	Treat. Effect (Cohen’s d)	Period Effect (t/P Value)	Period Effect (Cohen’s d)	Treat. × Period Effect (t/P Value)	Treat. × Period Effect (Cohen’s d)
Objectively Measured Sleep
TST	0.92	t(27) = 0.10, P = .92	d = 0.02	t(53.61) = 0.27, P = .80	d = 0.07	t(26) = 1.58, P = .13	d = 0.60
SOL	0.3	t(27) = 0.15, P = .89	d = 0.03	t(55) = 0.07, P = .94	d = 0.02	t(26) = −2.34, P = .03	d = 0.90
WASO	−0.96	t(27) = −0.45, P = .66	d = −0.08	t(52.436) = 0.02, P = .99	d < 0.001	t(26) = 0.83, P = .41	d = 0.32
Subjectively Measured Sleep
TST	4.35	t(27) = 0.75, P = .46	d = 0.14	t(51.653) = −0.21, P = .83	d = −0.06	t(26) = 0.39, P = .70	d = 0.15
SOL	0.52	t(25) = 0.28, P = .78	d = 0.05	t(47.08) = −0.34, P = .74	d = −0.09	t(24) = −0.58, P = .57	d = −0.23
SQ	0.21	t(26) = 1.97, P = .06	d = 0.38	t(46.87) = 1.19, P = .24	d = 0.32	t(25) = 1.55, P = .13	d = 0.61

mean diff. = mean difference, SOL = sleep onset latency, SQ = sleep quality, treat. = treatment, TST = total sleep time, WASO = wake after sleep onset; WB-UB = weighted blanket-usual (unweighted) blanket.

For objective SOL, the mean difference between the blankets was approximately 18 seconds longer during use of the WB compared to the UB; a nonstatistically significant difference based on a small effect, t(27) = 0.14512, P = .88, d = 0.03. Likewise, the period effect was nonsignificant and small, t(55) = 0.07, P = .94, d = 0.02. However, there was a statistically significant blanket × period interaction based on a large effect, t(26) = −2.34, P = .02, d = −0.90, indicating the presence of a potential carryover effect for 1 of the blanket types. We therefore analyzed the mean difference between WB and UB participants during Period 1 to better understand this interaction. However, the difference was nonsignificant and small in size, t(20.24) = −0.38, P = .70, d = 0.15.

For objective WASO, the mean difference between the blanket types was approximately 1 minute less during use of the WB compared to the UB; a nonstatistically significant difference based on a small effect, t(27) = −0.44, P = .65, d = −0.08. Likewise, both the period effect, t(52.43) = 0.01, P = .98, d < 0.001, and the blanket × period interaction effect, t(26) = 0.83, P = .41, d = 0.32 were nonsignificant and small in size.

Subjective sleep outcomes

Three sleep variables were examined from sleep diaries: TST, SOL, and morning rating of sleep quality. For TST, the within-subjects mean difference between the blanket types was 4.36 minutes longer for the WB compared to the UB; a nonstatistically significant difference based on a small effect, t(27) = 0.75, P = .45, d = 0.14. The period effect, t(51.65) = −0.21, P = .83, d = −0.06, and blanket × period interaction effect were also nonsignificant and small in size, t(26) = 0.39, P = .70, d = 0.15.

For subjective SOL, the within-subjects mean difference between the blanket types was 31 seconds longer for the WB vs the UB; a nonsignificant difference based on a small effect, t(25) = 0.28, P = .78, d = 0.06. The period, t(47.07) = −0.33, P = .7398, d = −0.09, and blanket × period interaction effects, t(24) = −0.58, P = .56, d = −0.23, were also small and nonsignificant.

The within-subjects mean difference in subjective sleep quality between the blanket types was slightly higher (0.21) for the WB compared to the UB. This effect was small but just failed to reach statistical significance, t(26) = 1.97, P = .06, d = 0.38. The period effect was nonsignificant and small, t(47) = 1.19, P = .24, d = 0.32, whereas the blanket × period interaction was nonsignificant but medium in size, t(25) = 1.55, P = .13, d = 0.61. To better understand this potential carryover effect, we analyzed the mean difference in sleep quality scores between the blanket types during Period 1 using a Wilcox test. A significant difference was detected indicating that participants who used the WB during Period 1 rated their sleep quality higher than participants using the UB during this period (P = .01).

Age, sex, and participation timing

Finally, we explored the potential impact of child age, sex, timing of participation (school year vs summer/school break) and maltreatment/trauma history on outcomes during use of the 2 blanket types. Age was dichotomized to compare outcomes between younger (6–10 years) and older (11–15 years) youth, and median split of CATS scores was used for maltreatment/trauma history. There was no evidence that any sleep outcomes differed for the WB vs UB based on age, sex, participation timing or CATS scores (all P’s > .05).

DISCUSSION

WBs have increased in popularity in recent years as a potential tool for improving sleep in various populations. Although empirical data are limited, prevailing theories suggest that WBs may improve sleep via calming effects secondary to parasympathetic activation, serotonin release, reduction in cortisol levels, and/or activation of the oxytocinergic system. It has also been suggested that use of a WB might simulate a hug or embrace, generating feelings of security and safety. Because childhood maltreatment and trauma are closely associated with sleep disturbances thought to emerge via hyperarousal of stress response systems, attachment disruptions, and self-regulatory deficits, we explored, for the first time, whether use of a WB for sleep might improve objective and/or subjective sleep outcomes among a sample of youth adopted from foster care (ie, with a history of some form of maltreatment). We utilized a randomized crossover design rather than a between-groups comparison trial because the former offers the advantage of intraindividual comparison, allowing us to estimate effects more precisely while maximizing statistical power.

Contrary to our hypotheses, better sleep was not detected based on either actigraphy or subjective sleep diaries when children used a WB compared to their usual blanket. There also was no indication that child age, sex, or timing of participation (school year vs summer months) impacted sleep outcomes. We did however find evidence of a blanket × period effect, such that youth who used the WB first reported slightly better sleep quality than participants who used their UB first. Based on the nature of the study, children were unavoidably aware of when they were using the WB and an inability to blind participants to condition increases the probability of a placebo response. Although our results do not provide evidence of an overall placebo effect, psychological factors likely explain why youth randomized to use the WB first (but not second) reported modestly better sleep quality compared to their usual blanket. For example, our research team’s observations indicated that children were generally more enthusiastic about using the WB when first enrolled in the study compared to 2 weeks later, which may have impacted expectations of the blanket’s effects on sleep. This result underscores the importance of using within subjects designs as well as objective measures in studying the efficacy of WBs on various outcomes.

The heterogeneity of experiences among children who have spent time in foster care must also be considered and may have contributed to null findings in the current study. Beyond specific types of abuse, neglect, and trauma exposure, children in our sample surely differ in terms of age at the time of placement in foster care, reasons for removal from biological parents, number of foster placements, and age at the time of adoption. The latter variable may be particularly relevant and to our knowledge has not been considered in prior sleep research among adopted children. It is not possible to understand precisely how these interindividual differences impact sleep-based outcomes in a relatively small sample, but this represents a critical question for future studies.

Additionally, it may be surprising that the average CATS score in our study fell below the clinical cutoff for trauma symptoms. While the CATS measure assesses a range of interpersonal traumas (eg, physical abuse, sexual abuse, witnessing violence) it does not inquire about critical forms of adversity (eg, homelessness, food insecurity) and neglect (eg, medical, physical, emotional). Because neglect is the most common reason children in the United States are placed in foster care,⁴⁸ these scores likely provide an underestimation of trauma exposure in the current sample. At the same time, low CATS scores could reflect the absence of posttraumatic stress symptoms and overactive hypothalamic-pituitary-adrenal responses linked with sleep disruption, potentially reducing the efficacy of WBs among maltreated children.

Our study has several limitations. Most importantly, our sample size was small and we were generally underpowered to detect statistically significant differences, increasing the possibility of type II error. For this reason, we also examined effect sizes and mean differences in objective and subjective sleep variables to identify the presence of potentially meaningful relationships. In addition to small to medium effect sizes, differences in objective and subjective sleep variables were generally less than 1 minute, suggesting the presence of normal variation and absence of any meaningful changes in sleep based on blanket type. Also, consistent with the population studied, most children in our study had at least 1 psychiatric disorder and were taking prescription medication. Although typical of the population studied, it remains unclear how specific diagnoses and medications might impact results. Despite efforts and procedures to ensure adherence, it is not possible to confirm that children used the blankets as prescribed during the study. Video monitoring, which would likely be considered invasive, would be required to ensure adherence in the home setting. Lastly, we did not include a washout period between the 2 assessment periods since children’s usual blanket served as the control blanket in our study. We did, however, exclude the first 3 nights of data collection from each assessment period from our analyses to allow for adjustment to each blanket and reduce potential carryover effects.

Several questions remain for future studies. First, along with larger sample sizes, longer measurement periods and more homogeneous groups of children, such as those who have experienced a particular type of trauma (eg, sexual or physical abuse) might reveal important findings. The role of other variables, including race/ethnicity, duration in foster care, number of placements, and time since adoption should also be considered. Further, beyond sleep parameters, measures of arousal, both objective and subjective, could offer insights into underlying mechanisms, which remain poorly understood. Finally, examining potential changes in specific types of child sleep problems (eg, Child Sleep Habits Questionnaire subscale scores) based on blanket type might guide more targeted interventions.

CONCLUSIONS

While accumulating evidence suggests WBs might improve sleep among some individuals, controlled studies are far more limited, particularly among children. Using a within-subjects crossover design including both actigraphy and subjective reports, we examined for the first time whether use of a WB improved the sleep of a sample of children with a history of maltreatment and clinical levels of sleep problems. Contrary to hypotheses, we did not, however, find evidence that a WB meaningfully improved any aspect of sleep compared to children’s usual blanket. Further, evidence of a placebo effect was detected when children used the WB at the start of the study compared to later, highlighting the overall importance of measuring and accounting for potential expectation effects in future studies. Research based on larger, more homogenous samples is needed.

DISCLOSURE STATEMENT

All authors have read and approved of the manuscript. Weighted blankets were provided by Luna Blankets. The authors report no conflicts of interest.

ABBREVIATIONS

ADHD

attention-deficit/hyperactivity disorder

CATS

Child and Adolescent Trauma Screen

SOL

sleep onset latency

TST

total sleep time

UB

usual (unweighted) blanket

WASO

wake minutes after sleep onset

WB

weighted blanket