Table 2.

Clinical studies on sleep disturbances in autism spectrum disorder in children

Authors (Ref.) country	Study design	Sample size	ASD assessment	Sleep–wake cycle assessment	Results	Major limitations
Hoshino et al. (62) Fukushima Japan	Case–control study	75 children with autism (3–15 years); 75 TD children (3–11 years).	WHO and Kanner’s diagnostic criteria; Infantile Developmental Test.	Sleep pattern was checked by the parents day-to-day for 1 month.	65% of autistic children showed sleep disturbance, no gender differences. Poorly developed autistic children showed a higher rate of sleep disturbance vs. well-developed autistic children.	No psychometric assessment of sleep pattern.
Richdale and Prior (63) Australia	Case–control study	39 children with autism (32 months–19 years): IQ < 55 (low-functioning, N = 12) vs. IQ > 55 (higher-functioning, N = 27); 35 TD children.	DSM-III diagnostic criteria. IQ: Leiter International Performance Scale or Bayley Infant Development Scales or Mertill-Palmer Scale of Mental Tests.	Parents completed 14-day sleep diaries and questionnaires.	During childhood, most of the children with autism experienced sleep problems: extreme sleep latencies, lengthy periods of night awakening, shortened night sleep, and early morning waking.	Small sample size; no evaluation of sleep parameters with standardized assessment.
Patzold et al. (64) Australia	Case–control study	31 children with autism; 36 TD children.	DSM-III or DSM-III-R diagnostic criteria.	A sleep diary completed by parents over a 2-week period; behaviors questionnaires.	Children with autism were likely to fall asleep later at night, have longer sleep latencies, sleep less at night, and spend a significant period of time awake during the night, compared with control group.	Small sample size; No evaluation of sleep parameters by standardized assessment.
Taira, Takase and Sasaki (65) Japan	Cross-sectional study	88 children with autism.	Clinical diagnosis.	Sleep questionnaires.	Sleep disorders were observed in 56 children, 44 of whom had sleep disorders before 3 years old. The most common problem was difficulty falling asleep, frequent awakening during sleep time, early morning awakening.	No control group; no evaluation of sleep and autism with standardized assessment.
Diomedi et al. (66) Roma, Italy	Cross sectional study	10 mentally retarded autistic subjects (12–24 years); 8 Down syndrome subjects; 8 TD subjects.	DSM-IV diagnostic criteria; CARS; Psychological Educational Profile (PEP).	Two consecutive overnight PSG.	Compared to normal subjects, autistic subjects presented a significant reduction of REM %, a fragmentation of REM periods, due to a frequent intrusion of NREM 1 and 2, an increased number of awakenings with a consequent reduction of Sleep Efficiency.	Small sample size.
Hering et al. (67) Israel	Comparative study	22 children with autism: 12 with sleep problems	Clinical diagnosis.	Sleep questionnaire; 72 h of actigraphy.	Autistic children showed early morning awakenings and multiple and night arousals	Small sample size; no evaluation of autism parameters by standardized assessment.
Godbout et al. (68) Canada	Case–control study	8 patients with AS (7–53 years); 8 TD age-/sex-matched subjects.	DSM-IV diagnostic criteria; ADI.	Sleep was recorded for two consecutive nights.	Patients with AS showed decreased sleep time in the first 2/3 of the night, increased number of shifts into REM sleep from waking, and REM sleep disruption; sleep spindles were significantly decreased.	Small sample size; use of medications.
Elia et al. (69) Italy	Comparative study	17 children and adolescents with ASD (5–16 years); 7 patients with mental retardation and fragile X syndrome; 5 TD subjects.	DSM-IV diagnostic criteria; karyotyping; neurometabolic screenings; brain imaging; Psychoeducational Profile-revised test (PEP-R); CARS.	Two overnight PSG with one adaptation night.	Density of REM was not significantly different in the three groups; some sleep parameters such as time in bed, and total sleep time were significantly lower in ASD subjects than in TD ones; CARS scores to visual response and nonverbal communication showed significant correlation with some sleep parameters.	Small sample size.
Honomichl et al. (70) California	Longitudinal study	100 children with PDD	Children were diagnosed with ASD, PDD not otherwise specified, AS, or other related disorders.	Two sleep diary data collection periods; CSHQ; Parenting Events Questionnaire.	All children with PDD exhibited longer sleep onset and greater fragmentation of sleep than that reported for age-matched community norms.
Wiggs and Stores (71) Oxford, UK	Cross-sectional study	69 children with ASD (aged 5 to 16 years).	ICD-10 diagnostic criteria.	Sleep histories from parents; Simonds and Parraga Sleep Questionnaire; 2-week sleep diary; actigraphy for five nights.	Parent-reported sleeplessness (64%). Sleep disorders underlying the sleeplessness were most commonly behavioral; sleep patterns measured objectively did not differ between those children with or without reported sleeplessness, but the sleep quality of all children seemed to be compromised compared with normal values.	Sample included children of various ages and intellectual levels.
Gail Williams, P et al. (72) England	Cross-sectional study	210 children with autism.	DSM-IV diagnostic criteria; Wechsler Intelligence Scale for Children, 3ed; Differential Ability Scales Mental Retardation (MR).	Likert-based questionnaire for parent report.	Sleep problems reported: difficulty in falling asleep, restless sleep, not falling asleep in own bed, and frequent wakings, sleepwalking, morning headaches, crying during sleep, apnea, and nightmares. No significant differences were identified in frequencies of reported sleep problems between MR and not MR groups.	No evaluation of sleep parameters by objective measures.
Schreck et al. (73) USA	Cross-sectional study	55 children with autism (5–12 years).	Gilliam Autism Rating Scale (GARS).	Parental report sleep questionnaire.	Children with strong responses to the environment at night and who tend to awaken at night show more markedly autistic-type communication patterns on the GARS.	No evaluation of sleep parameters by objective measures.
Polimeni et al. (74) Australia	Cross-sectional study	53 children with autism; 53 children with AS; 66 TD children.	Clinical diagnosis.	The Behavioral Evaluation of Disorders of Sleep (BEDS).	High prevalence of sleep problems with significantly more problems reported in the autism and AS groups.	No evaluation of sleep and autism parameters by standardized measures; use of medication.
Cotton & Richdale (75) Australia	Case–control study	153 children: 98 had an ID, 37 with autism, 15 with Down syndrome, 29 with Prader–Willi syndrome, and 29 with intellectual disability; 55 TD subjects.	Clinical diagnosis.	Parental report sleep questionnaire.	Sleep problems were more prevalent in autism than the other disorders. Sleep maintenance problems were common in autism.	Small sample size; no evaluation of sleep and autism parameters by standardized measures.
Allik et al. (76) Stockholm, Sweden	Case–control study	32 school-age children with AS and HFA; 32 TD age- and gender-matched children.	Clinical diagnosis; ASSQ.	Parent-Reported Sleep Problems; 1-week parent recorded Child Sleep Diary; 1-week actigraphy.	Parental report, sleep diary, and actigraphy showed that children in the AS/HFA group spent longer time awake in bed before falling asleep than the control group.	Small sample size; use of medication.
Allik et al. (77) Stockholm, Sweden	Case–control study	32 school-age children with AS and HFA; 32 TD age-/gender-matched children	Clinical diagnosis; ASSQ; Strengths and Difficulties Questionnaire.	Parent-reported sleep problems; 1-week parent-recorded Child Sleep Diary; 1-week actigraphy.	Parent-reported difficulties initiating sleep and daytime sleepiness were more common in children with AS/HFA than in controls. Children with insomnia showed more parent-reported autistic and emotional symptoms, and more teacher-reported emotional and hyperactivity symptoms than those without insomnia.	Small sample size; use of medication.
Krakowiak et al. (78) California	Case–control study	303 children with ASD; 63 children with other developmental delays (DD); 163 TD children. The mean age was 3.6 years.	ADI-R; ADOS. Cognitive and adaptive functioning was assessed with specific scales.	Parent-administered questionnaire.	53% of children with ASD showed at least one sleep problem, followed by 46% of children with DD, and 32% of the TD group. Children with ASD had higher problems with sleep onset and higher night awakening compared to the TD group. Sleep disturbances of ASD group were not associated with cognitive and⁄or adaptive delays.	No evaluation of sleep parameters by standardized measures.
Liu et al. (79) USA	Comparative study	108 children with ASD, 27 children with AS; 32 with other diagnoses of ASD.	Parental report diagnosis of ASD; ADOS-G.	CSHQ; A structured sleep and family demographic questionnaire.	86% of children had at least one sleep problem almost every day, including 54% with bedtime resistance, 56% with insomnia, 53% with parasomnias, 25% with sleep disordered breathing, 45% with morning rise problems, and 31% with daytime sleepiness. Individual sleep problems: restless during sleep (28.7%), difficulty falling asleep (28.1%), awakened by others in the morning (26.9%), bed-wetting (26.3%), and poor appetite in the morning (25.7%).	Lack of a control group.
Malow et al. (80) Nashville, TN	Cross-sectional study	21 children with ASD; 10 TD children (4–10 years).	DSM-IV-TR diagnostic criteria; Clinical diagnosis; ADOS; CBCL; Peabody Picture Vocabulary Test (PPVT).	CSHQ; sleep histories; 1-week sleep diaries; 2 consecutive nights of video monitoring combined with EEG and PSG.	Poor sleepers showed prolonged sleep latency and decreased sleep efficiency on night 1 of PSG and differed on insomnia-related subscales of the CSHQ (increased sleep onset delay and decreased sleep duration) and also affective and reciprocal social problems on the CBCL and the ADOS, respectively.	Small sample size.
Miano et al. (81) Italy	Case–control study	31 patients with ASD: 17 with I.Q. 25–40 4 with I.Q. 40–55 (3.7–19 years); 893 TD children and adolescents.	DSM-IV diagnostic criteria; CARS; Wechsler Intelligence Scale for Children Revised or Weschsler Adult Intelligence Scale.	Parental report sleep questionnaire; PSG (16 patients and 18 controls).	ASD children showed high prevalence of initiating and maintaining sleep problems, enuresis, repetitive behavior when falling asleep, daytime sleepiness. PSG: ASD children showed reduced time in bed, total sleep time, sleep period time and REM latency.
Bruni et al. (82) Rome, Italy	Cross-sectional study	8 children with AS; 10 children with autism, 12 TD children.	ADOS; CBCL; Wechsler Intelligence Scale for Children—Third Edition Revised-WISC-III	Sleep Questionnaire; Pediatric Daytime Sleepiness Scale; PSG	AS children showed high prevalence of initiating and maintaining sleep problems and daytime sleepiness. Subjects with AS showed increased CAP rate in SWS and A1 percentage. In subjects with AS, verbal IQ had a significant positive correlation with total CAP rate and CAP rate in SWS and with global and SWS A1 index. The percentage of A2 negatively correlated with full-scale IQ, verbal and performance IQ. CBCL total score correlated positively with CAP rate and A1 index while externalizing score correlated negatively with A3%.	Small sample size.
DeVincent et al. (83) New York	Case–control study	112 children with PDD (49 with autistic disorder, 13 with AS, and 50 with PDD–not otherwise specified); 497 TD children.	DSM-IV diagnostic criteria; Early Childhood Inventory–4; ADOS.	Early Childhood Inventory–4.	18% of children with PDD met the criteria for sleep disturbance. There were no significant differences between PDD subtypes in either the rate or severity of sleep problem. Sleep-disturbed children in both samples exhibited more severe behavioral difficulties than children without sleep problems.	No evaluation of sleep parameters by objective measures.
Dominick et al. (84) USA	Retrospective study	39 children with a history of language impairment (HLI); 67 children with ASD.	DSM-IV diagnostic criteria; ADI-R; ADOS-G.	The Atypical Behavior Patterns Questionnaire-parental reported.	Over 2/3 of the children with autism experienced atypical patterns of sleep. Initial insomnia and middle insomnia each occurred in >50% of the children with ASD. 12% of the sleep-disturbed children with ASD have terminal insomnia. The presence of sleep disturbances in children with autism and with HLI combined was significantly related to the presence of depression.	Use of retrospective questionnaire; interviewers were not blind to the participant’s diagnosis; sample was not chosen at random.
Allik et al. (85) Stockholm, Sweden	Case–control study	16 school-age children with AS and HFA; 16 TD age-/gender-matched children.	Clinical diagnosis.	1-week actigraphy.	At follow-up (2–3 years after the baseline), children with AS/HFA showed longer night waking and lower sleep efficiency during weekends than the controls.	Small sample size; use of medication.
Goodlin-Jones et al. (86) California	Comparative study	68 children with autism; 57 children with developmental delay without autism (DD); 69 TD children (2.0–5.5 years).	ADOS; Test of cognitive ability and of adaptive functioning; ADI-R.	Actigraphy; sleep diary; CSHQ.	DD group after sleep onset exhibited more and longer awakenings than the other two groups. Autistic children exhibited less total sleep time/24 h than the other two groups. Parent reports of sleep problems were higher in the AUT and DD groups than the TD group, but parent reports did not concur with more objective measures for behavioral insomnia.	Results may not generalize to a more heterogeneous population-based, community sample or to children referred for a clinical sleep disorder. The CSHQ has not been validated for these ages.
Goodlin-Jones et al. (87) California	Comparative study	68 children with autism; 57 children with developmental delay without autism [DD]; 69 TD children (2.0–5.5 years).	ADOS; Test of cognitive ability and of adaptive functioning; ADI-R.	Children were studied on three occasions, separated by a 3-month interval. At each assessment: actigraphy for 1 week; sleep–wake diaries; CSHQ.	Both neurodevelopmental groups showed more sleep problem by actigraphy and the CSHQ than TD children. Sleep onset insomnia and night awakenings decreased respectively by 40% and 30% every 3-month periods of actigraphic records.
Goodlin-Jones et al. (88) California	Comparative study	68 children with autism, 57 children with developmental delay without autism [DD]; 69 TD children (2.0–5.5 years)	Mullen Scales of Early Learning; Vineland Adaptive Behavior Scale; ADOS; ADI-R; Social Communication Questionnaire.	Actigraphy; sleep diary; CSHQ.	CSHQ was clinically useful for screening of sleep problems in TD young children as well as in children with diverse neurodevelopmental diagnoses; sleep problems were prevalent in young children.
Paavonen J et al. (89) Finland	Case–control study	52 children with AS; 61 TD subjects (5–17 years).	DSM-IV or ICD-10 diagnostic criteria; CBCL; ASSQ.	Sleep Self-Report.	Problems with sleep onset and maintenance, sleep-related fears, negative attitudes toward sleeping, and daytime somnolence were more frequent in AS vs. TD. Short sleep duration was almost twofold (59% vs. 32%) in AS vs. TD; the risk for sleep onset problems was fivefold (53% vs. 10%) more common in AS vs. TD.	No evaluation of sleep parameters by standardized measures.
Souders et al. (90) Philadelphia, PA	Descriptive cross-sectional study.	59 children with ASD (26 with autism, 21 with PDD-NOS, and 12 with AS) (4–10 years); 40 TD subjects.	DSM-IV-TR diagnostic criteria; ADOS; Children enrolled as TD were screened with Social Communication Questionnaire (SCQ) and developmental history.	CSHQ; 17-day parental report sleep diaries; 10-nights of actigraphy.	66.1% of parents of children with ASD and 45% of parents of the control group reported sleep problems in their sons; 66.7% of children with ASD (75% autism, 52.4% PDD-NOS, 75% AS) and 45.9% of the control subjects had disturbed sleep by actigraphy.	No evaluation of sleep parameters by standardized measures; small sample size
Goldman et al. (91) Nashville, TN	Case–control study	42 children with ASD without intellectual disability (4 to 10 years); 16 age-compared TD children.	DSM-IV-TR diagnostic criteria ADOS; Repetitive Behavior Scales–Revised (RBS–R); Peabody Picture Vocabulary Test–III (PPVT–III).	CSHQ; Parental Concerns Questionnaire (PCQ); CBCL; Actigraphy: PSG.	ASD poor sleepers differed from ASD good sleepers on actigraphy (sleep latency, sleep efficiency, fragmentation) and PSG (sleep latency) measures, reporting inattention, hyperactivity, and restricted/repetitive behaviors. Fragmentation was correlated with more restricted/repetitive behaviors.	Parental measures to differentiate the poor and the good sleepers groups; small sample size.
Buckley et al. (92) New York	Comparative study	60 children with autism; 13 children with developmental delay; 15 children with TD (2–13 years)	ADOS; ADI-R.	CSHQ; PSG.	No differences between TD vs. developmental delay groups. Comparison of autistic children vs. TD children revealed short total sleep time, great slow-wave sleep percentage, and small REM sleep percentage (14.5% vs. 22.6%) in ASD ones.	Use of medications.
Giannotti et al. (93) Rome, Italy	Comparative study	22 children with non-regressive autism; 18 children with regressive autism; 12 TD children (5–10 years).	DSM-IV TR diagnostic criteria; ADI-R; ADOS-G; nonverbal IQ > 50 assessed by Leiter International Performance Scale.	CSHQ; an overnight PSG.	Regressed children reported high CSHQ score: bedtime resistance, sleep onset delay, sleep duration and night wakings. Regressive subjects had significantly less efficient sleep, less total sleep time, prolonged sleep latency, prolonged REM latency and more time awake after sleep onset than non-regressive and TD group.	Small sample size; no evaluation of sleep parameters by standardized measures; small sample size.
Anders et al. (94) Sacramento, CA	Case–control study	68 children with autism (ASD); 57 children with DD without ASD; 69 TD children.	ADOS; ADI–R.	Actigraphy for 7 consecutive days for each of the 3 recording weeks (initial evaluation, 3 months later, and again after 3 months) During each 7-day week, parents completed a daily sleep diary.	ASD group slept less per 24-h period and were less likely to awaken at night than children in the other two groups. Children in the DD group had more frequent and longer duration nighttime awakenings than children in the ASD group. Children in the two neurodevelopmentally disordered groups demonstrated more night-to-night variability in their sleep–wake measures than children in the TD group.
Rzepecka et al. (95) UK	Cross-sectional study	187 children with ID and/or ASD.	ADOS; Developmental, Dimensional and Diagnostic Interview (3DI).	CSHQ; Spence Children’s Anxiety Scale-Parent Version (SCAS-P); Aberrant Behaviour Checklist-Community (ABC-C).	Significant positive correlations between sleep problems, challenging behaviors and anxiety in children with ID and/or ASD.	No evaluation of sleep parameters by standardized measures; small sample size
Schwichtenberg et al. (96) California	Comparative study	68 children with autism; 57 children with DD; 69 TD children (24–66 months).	ADOS; ADI-R; Mullen Scales of Early Learning (MSEL); General adaptive behavior scales.	7 consecutive 24-h periods of actigraphy; parent-report sleep–wake diary. Sleep was assessed for 7 consecutive days on 3 separate occasions over 6 months.	Children with autism napped less often and for shorter periods of time than children with DD Children with DD napped more like children in the TD group, who were 6 months younger. Each group displayed an expected shift in daytime sleep as more children matured out of their naps.	Lack of specific groups of intellectual disability.
Anders et al. (97) Sacramento, CA	Case–control study	68 children with autism (AUT); 57 children with DD without AUT; 69 TD children.	ADOS; ADI–R; Psychoeducational Profile—Revised (PEP-R); Bayley pegboard task; CBCL.	7 consecutive 24-h periods of actigraphy for each of the 3 recording weeks (initial evaluation, 3 months later and again after 3 months). During each 7-day week, parents completed a daily sleep diary.	Both autism and ID groups showed poorer daytime performance and behaviors than the TD one. These significant differences persisted over 6 months; long night awakenings and lower sleep efficiency predicted daytime sleepiness in the ID group; parent-report sleep problems were associated with daytime sleepiness and behavior problems.	No developmentally tests of daytime functioning valid for NDD and TD preschool-age children.
Goldman et al. (98) USA	Cross-sectional study	1,859 children of the Autism Treatment Network	DSM-IV-R diagnostic criteria; ADOS.	CSHQ; Parents Concerns Questionnaire.	Adolescents reported delayed sleep onset, short sleep duration, and daytime sleepiness; while toddlers reported bedtime resistance, sleep anxiety, parasomnias, and night wakings.	No evaluation of sleep parameters by standardized measures.
Sikora et al. (99) Colorado	Cross-sectional study	1193 children with ASD.	General adaptive behavior scales; Survey Interview Form, Second Edition; CBCL.	CSHQ.	ASD group with sleep problems showed internalizing and externalizing behavior problems, and poor adaptive skill development. Children with moderate to severe sleep problems had greater behavior difficulties.
Taylor et al. (100) USA	Cross-sectional study	335 children with autism or PDD-NOS (1–10 years).	General adaptive behavior scales.	Behavioral evaluation of sleep disorders.	Children who slept fewer hours per night had lower overall intelligence, verbal skills, overall adaptive functioning, daily living skills, socialization skills, and motor development. Children who slept fewer hours at night with waking during the night had more communication problems. Breathing-related sleep problems and fewer hours of sleep related most often to problems with perceptual tasks.	No evaluation of sleep parameters by objective measures.
Siversten et al. (101) Norway	Longitudinal study	3700 children, of whom 28 have ASD.	ASSQ.	Parent-reported sleep problems; Strengths and Difficulties Questionnaire (SDQ).	In the ASD group, the prevalence of chronic insomnia was more than 10 times higher compared to controls. ASD was a strong predictor of sleep problems and emotional and behavioral problems explained a large proportion of this association.	No evaluation of sleep parameters by objective measures; no measure of the severity of the sleep problems.
Baker et al. (102) Australia	Comparative study	34 adolescents with HFASD (14–17 years); 27 TD adolescents.	Social Communication Questionnaire.	7-day sleep diary; actigraphy in 55% of adolescents with HFASD; Sleep Habits Survey, adapted from the School Sleep Habits Survey; Pediatric daytime sleepiness scale; flinders fatigue scale.	Adolescents with HFASD were 3 times more likely to report a sleep problem than their TD peers (46.2% vs. 14.8%). Adolescents with HFASD had decreased sleep efficiency, and more fatigue compared with TD adolescents. While TD adolescents generally experienced one symptom of insomnia, adolescents with HFASD were likely to experience 2 or 3 symptoms of insomnia.	Small sample size.
Hollway et al. (103) USA	Cross-sectional study	1583 children in the Autism Treatment Network (2–17 years).	DSM-IV diagnostic criteria; ADOS;CBCL; Mullen Scales of Early Learning (MSEL); Stanford-Binet Intelligence Scale: Fifth Edition.	Short Sensory Profile; CSHQ.	Anxiety, autism symptoms severity, sensory sensitivities, and GI problems were associated with sleep disturbances. IQ positively predicted sleep disturbance and children with AS were more vulnerable than others.	No evaluation of sleep parameters by objective measures.
Humphreys et al. (104) UK	Cross-sectional study	30 children with classical childhood autism; 15 children with atypical autism; 23 children with AS.	Social Communication Disorders Checklist; Wechsler Intelligence Scale for Children 3rd edition (WISC-III).	Parental report sleep questionnaires.	From aged 30 months to 11 years old, children with ASD slept for 17–43 min less each day than contemporary controls. No significant difference in total sleep duration was found in infancy, but from 30 months of age, children with ASD slept less than their peers. Nighttime sleep duration was shortened by later bedtimes and earlier waking times.	Small sample size; absence of a control group.
Nadeau et al. (105) USA	Cross-sectional study	102 children and adolescents with ASD and comorbid anxiety disorders (7–16 years).	ADI-R; ADOS; Social Responsiveness Scale (SRS) measuring severity of autism spectrum symptoms; Anxiety Disorders Interview Schedule; Pediatric Anxiety Rating Scale; Multidimensional Anxiety Scale for Children–Parent; report measuring of anxiety symptoms.	CBCL.	The number of sleep-related problems endorsed directly associated with parent ratings of social deficits, internalizing and externalizing symptoms, and anxiety symptoms, as well as with clinician-rated anxiety symptoms.	No evaluation of sleep parameters by objective measures; absence of a control group.
Richdale et al. (106) Australia	Case–control study	27 adolescents with HFASD (14–17 years); 27 age-/sex-matched TD adolescents (14–17 years).	The Centre for Epidemiological studies Depression scale; the anxiety subscale of the Depression, Anxiety and Stress Scale.	7-day sleep/wake diary. 55% of HFASD adolescents and all TD adolescents wore an actigraphy concurrently with the sleep diary. Sleep Habits Survey; Chronic Sleep Reduction Questionnaire; Sleep Anticipatory Anxiety Questionnaire (SAAQ) to measure pre-sleep arousal.	Adolescents with HFASD had significantly higher scores for sleep arousal compared with TD adolescents, and poorer daytime functioning. There were significant correlations between sleep variables and psychopathology variables the HFASD group, than in the TD group.	Small sample size.
Hodge et al. (107) San Bernardino, CA	Comparative study	108 children with ASD; 108 TD children (3–18 years).	Clinical diagnoses; Autism Index; Gilliam Autism Rating Scale-2.	CSHQ.	Poor sleep quantity and quality in children with ASD, particularly children aged 6–9 years. The sleep problems of children with ASD were unlikely to diminish with age.
Tudor et al. (108) USA	Cross-sectional study	62 children with ASD	Parent-reported diagnosis; Non-Communicating Children’s Pain Checklist–Revised.	CSHQ.	93% of the sample scored above 41 on the CSHQ. Pain predicted overall sleep disturbance and three specific sleep problems: sleep duration, parasomnias, and sleep-disordered breathing. These specific sleep problems were predicted by specific modalities of nonverbal pain communication.	Parental report of diagnosis and all data.
May et al. (109) Australia	Case–control study	46 children with ASD; 38 TD children (7–12 years).	DSM-IV-TR diagnostic criteria; Social Responsiveness Scale; Wechsler Intelligence Scale for Children-Fourth Edition; Spence Children’s Anxiety Scale.	CSHQ.	The ASD group had more sleep disturbance than the TD group. Sleep disturbance at baseline predicted later anxiety. Sleep disturbance decreased over the year in children with ASD, but not in TD children. Reduced sleep disturbance was associated with improved social ability.	No evaluation of sleep parameters by objective measures; only high-functioning children analyzed.
Mazurek & Petrosky (110) USA	Cross-sectional study	1347 children and adolescents enrolled in the Autism Speaks Autism Treatment Network.	ADOS; CBCL; Short Sensory Profile.	CSHQ.	Anxiety was associated with all types of sleep problems (bedtime resistance, sleep-onset delay, short sleep duration, sleep anxiety, and night waking). Sensory responsivity was correlated with sleep problem, but it was not significantly associated with bedtime resistance or sleep anxiety for younger children.	No evaluation of sleep parameters by objective measures; absence of a control group.
Wang et al. (111)	Cross-sectional study	60 Chinese children with ASD (6–17 years).	DSM-IV-TR diagnostic criteria.	CSHQ; Strengths and Difficulties Questionnaire.	Sleep disturbances were severe and common, with rates of 70.0% for overall disturbances and 15.0% (daytime sleepiness) to 40.0% (sleep duration) for specific domains. Female gender, older parental age, higher hyperactivity, and poorer prosocial behavior were associated with increased overall sleep disturbances.	Absence of a control group; no evaluation of sleep parameters by objective measures.
Hirata et al. (112) Japan	Case–control study	965 community; 193 preschoolers with ASD	DSM-5 diagnostic criteria; ADOS-G; CBCL.	Japanese Sleep Questionnaire for Preschoolers.	Preschoolers with ASD had more sleep problems, including OSA, than those in the community, sleep problems, especially insomnia, correlated with behavioral problems in preschoolers with ASD.	No evaluation of sleep parameters by objective measures.
Hundley et al. (113) New York	Cross-sectional study	532 children with ASD (2–17 years).	DSM-IV-TR diagnostic criteria; ADOS; ADI-R; CBCL.	CSHQ.	Repetitive sensor/motor behaviors were positively associated with parent-reported sleep problems, and the relationship remained significant after controlling for anxiety symptoms. Insistence on sameness was not significantly associated with sleep problems.	No evaluation of sleep parameters by objective measures; absence of a control group.
Irwanto et al. (114) Indonesia and Japan	Cross-sectional study	50 children with ASD.	DSM-5 diagnostic criteria.	CSHQ.	There were significant differences in total night and early awakenings between Indonesian and Japanese children.	Small sample size; absence of a control group. No evaluation of sleep parameters by objective measures.
Fletcher et al. (115) England	Case–control study	21 children with ASD; 29 TD children.	DSM-IV-TR diagnostic criteria; Spence Children’s Anxiety Scale; Social Worries Questionnaire; Bedtime Routines Questionnaire	CSHQ; 14 nights of actigraphy	There was a significant reduction in sleep duration over time in both groups, and the ASD one showed more night-to-night variability in sleep quality. Reductions in actigraphy-derived sleep efficiency were associated with an increased frequency of maladaptive activities in the hour before bedtime, in children with and without ASD.	Small sample size.
Mazurek et al. (116) New York	Cross-sectional study	81 children with ASD.	Physical Aggression and the Hostility subscales of the Children’s Scale for Hostility and Aggression: Reactive/Proactive (C-SHARP); the Inattention and the Hyperactivity subscales of the Vanderbilt Attention Deficit/Hyperactivity Disorder Parent Rating Scale (VADPRS).	CSHQ.	Sleep problems were significantly associated with physical aggression, irritability, inattention, and hyperactivity. Night awakenings had the most consistently strong association with daytime behavior problems, even after controlling for the effects of age and sex.	No evaluation of sleep parameters by standardized measure.
Kheirouri et al. (117) Turkey	Case–control study	35 children with autism; 31 TD subjects	DSM-IV-TR diagnostic criteria.	CSHQ.	There was no significant association between GI problems and autism severity, but a significant positive correlation have been found between different indicators of sleep disorders and severity of autism. Plasma levels of serotonin were significantly high in autistic children, but no significant association with sleep problems.	Small sample size; no evaluation of sleep parameters by standardized measure.
Mutluer et al. (118) Turkey	Case–control study	64 patients with ASD; 53 TD subjects.	DSM-IV-TR diagnostic criteria; CARS; CBCL.	Pediatric sleep questionnaire.	Children with ASD had higher frequency of sleep problems, snoring, breathing problems, behavioral problems compared with healthy children; sleep latency was prolonged in children with ASD compared with healthy subjects.	No evaluation of sleep parameters by standardized measures; no gender and other confounding factors examination.
Veatch et al. (119) USA and Canada	Cross-sectional	80 children with autism and sleep onset delay (2–10 years).	DSM-IV-TR diagnosis criteria; ADOS.	CSHQ; actigraphy.	Reported problems with sleep onset delay were concurrent with sleep duration problems in 66% of children, night wakings in 72% of children, and bedtime resistance in 66% of children; 38% of children reported insomnia. Parent reports and actigraphy results were in accordance.	Relatively small sample size.
Aathira et al. (120) New Delhi India	Longitudinal study	71 children with ASD; 65 TD children.	DSM IV diagnostic criteria; CARS; DP-3 (Developmental Profile-3).	PSG (48 subjects); CBCL.	The prevalence of poor sleepers among ASD and controls were 77.5% and 29.2%, respectively. The salient findings on PSG were reduced sleep efficiency, decreased REM and SWS duration 1. The CBCL score was significantly high in poor sleepers compared to good sleepers on CSHQ. There was no correlation of CARS or DP-3 score with sleep problems in ASD children.	Small sample size; PSG only for a night.
Kose et al. (121) Turkey	Retrospective cross-sectional study	48 children with ASD; 46 children with ID; 48 TD children (2–18 years).	DSM-5 diagnostic criteria; CARS; Wechsler Intelligence Scale for Children-Revised (WISC-R); Ankara Developmental Screening Inventory (ADSI).	CSHQ.	Children with NDD had a 2.8-fold increased risk of sleep disturbance, 3.1-fold increased risk for history of sleep disorders in parents, 3.3-fold increased risk for psychiatric comorbidity, 13.1-fold increased risk for co-sleeping with parents. Co-sleeping with parents and family history of sleep problems increased the risk of sleep disturbances.	No evaluation of sleep parameters by standardized measures; Turkish adaptations of ADI-R and ADOS are not yet available.
Sannar et al. (122) USA	Cross-sectional study	106 hospitalized children and adolescents with ASD (9.5–16.3 years).	Aberrant Behavior Checklist-Community (ABC-C); ADOS-2.	Sleep habits.	High scores on the ABC-C (irritability, stereotypy, and hyperactivity subscales) at admission were significantly associated with fewer minutes slept during the last five nights of hospitalization. There was no association between total awakenings and ABC-C scores or ADOS-2 comparison scores.	No evaluation of sleep parameters by standardized measures; absence of a control group.
Veatch et al. (123) USA	Cross-sectional	2714 children in the Simons Simplex Collection.	DSM-5 diagnostic criteria; ADI-R; ADOS; Differential Ability Scales, 2nd Edition; Mullen Scales of Early Learning.	Parental report of sleep; actigraphy; CBCL.	Sleep duration and severity of core ASD symptoms were negatively correlated, sleep duration and IQ scores were positively correlated. Severe social impairment was strongly associated with short sleep duration. Increased severity for numerous maladaptive behaviors, as well as reports of attention deficit disorder, depressive disorder, and obsessive compulsive disorder were associated with short sleep duration. Severity scores for social/communication impairment and restricted and repetitive behaviors were increased, IQ scores were decreased in children who reported to sleep 420 min per night compared to children sleeping 660 min.	No evaluation of sleep parameters by standardized measures; wide age range; use of medication.
Verhoeff et al. (124) Netherlands	Longitudinal study	5151 children (81 children with ASD)	DSM IV/5 diagnostic criteria; Pervasive Developmental Problems score (PDP) of the CBCL; Social Responsiveness Scale (SRS).	Sleep Problem Scale.	Sleep problems in early childhood were prospectively associated with a higher SRS score, but not when correcting for baseline PDP score. A higher SRS score and an ASD diagnosis were associated with more sleep problems at later ages, even when adjusting for baseline sleep problems. A trajectory of increasing sleep problems was associated with ASD.	No evaluation of sleep parameters by standardized measures; absence of a control group.

DSM, Diagnostic and Statistical Manual; ICD-10, International Classification of Diseases-10; ASD, autism spectrum disorder; AS, Asperger syndrome; HFA, high-functioning autism; PDD, pervasive developmental disorders; DD, developmental delay; CSHQ, Children’s Sleep Habits Questionnaire; CARS, Childhood Autism Rating Scale; ASSQ, The High-Functioning Autism Spectrum Screening Questionnaire; ADI, Autism Diagnostic Interview; ADOS, Autism Diagnostic Observation Schedules; PSG, polysomnography; CBCL, child behavior checklist; IQ, intelligence quotient; TD, typically development; WHO, World Health Organization; REM, rapid eye movement.