Genetic and environmental contributions to stability and change of sleep problems in toddlerhood

Heritability of Psychological Traits and Developmental Milestones in Infancy: A Systematic Review and Meta-analysis

IMPORTANCE

Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood.

OBJECTIVE

To synthesize the large twin study literature partitioning phenotypic variance in psychological traits and developmental milestones in infancy into estimates of heritability and shared and nonshared environment.

DATA SOURCES

PubMed, PsycINFO, and references of included publications were searched up to February 11, 2021.

STUDY SELECTION

Peer-reviewed publications using the classical twin design to study psychological traits and developmental milestones from birth to 2 years old were included.

DATA EXTRACTION AND SYNTHESIS

Data were extracted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and categorized using the International Classification of Functioning, Disability and Health: Children and Youth Version. Data were pooled in 3-level random effects models, incorporating within-cohort variance in outcome measurement and between-cohort variance. Data were analyzed from March 2021 through September 2021.

MAIN OUTCOMES AND MEASURES

The primary outcomes were monozygotic and dizygotic twin correlations. These were used to calculate genetic and shared and nonshared environment estimates.

RESULTS

Among 139 publications that were systematically retrieved, data were available on 79 044 twin pairs (31 053 monozygotic and 47 991 dizygotic pairs), 52 independent samples, and 21 countries. Meta-analyses were conducted on psychological traits and developmental milestones from 106 publications organized into 10 categories of functioning, disability, and health. Moderate to high genetic estimates for 8 categories were found, the highest of which was psychomotor functions (pooled h2, 0.59; 95% CI, 0.25-0.79; P < .001). Several categories of traits had substantial shared environment estimates, the highest being mental functions of language (pooled c2, 0.59; 95% CI, 0.24-0.86; P = .001). All examined categories of traits had moderate or high nonshared environment estimates, the highest of which were emotional functions (pooled e2, 0.42; 95% CI, 0.33-0.50; P < .001) and family relationships (pooled e2, 0.42; 95% CI, 0.30-0.55; P < .001).

CONCLUSIONS AND RELEVANCE

These findings may be an important source of information to guide future gene discovery research, public perspectives on nature and nurture, and clinical insights into the degree to which family history and environments may estimate major domains of infant functioning, disability, and health in psychological traits and developmental milestones.

Prevalence and stability of insufficient sleep measured by actigraphy: a prospective community study

BACKGROUND

It is well established that reduced sleep has detrimental effects on school-aged children's functioning, but the prevalence and stability of objectively measured insufficient sleep throughout childhood is unknown.

METHODS

A sample of 799 children was followed biennially with 24-h 7-day accelerometer (hip-placed) measurements from ages 6 to 12 years. Insufficient sleep was conceptualized as sleeping <7 h on average (AIS) and as the number of nights with <7 h of sleep (NNIS).

RESULTS

The prevalence of AIS ranged from 1.1% to 13.6%. Of those without AIS, 15.1-64.5% had >1 NNIS. At ages 6-10 years, NNIS was higher on weekend nights, but at age 12 years NNIS was lower on weekends (18.1%) compared to weekdays (23.4%). The stability of AIS was low from ages 6 to 8 years and from 8 to 10 years, but increased from age 10 to 12 years, whereas NNIS evidenced higher stability, increasing sharply through late middle childhood.

CONCLUSIONS

The prevalence of AIS was low during the preschool and early school years but increased toward preadolescence. The 2-year stability of insufficient sleep was very low when conceptualized as AIS and moderate when defined as NNIS, hence NNIS might be more sensitive than AIS. Insufficient sleep appears transient in middle childhood and thus might not warrant intervention unless it fosters impairment and endures.

Stability and Predictive Validity of the Parent-Child Sleep Interactions Scale: A Longitudinal Study Among Preschoolers

Little research has examined the processes underlying children's persistent sleep problems and links with later psychopathology. The current study examined the stability of parent-child sleep interactions as assessed with the parent-reported Parent-Child Sleep Interactions Scale (PSIS) and examined whether sleep interactions in preschool-age children predict sleep problems and psychiatric symptoms later in childhood. Participants included 108 preschool-age children (50% female) and their parents. Parents completed the PSIS when children were 3-5 years (T1) and again when they were 6-9 years (T2). The PSIS includes three subscales-Sleep Reinforcement (reassurance of child sleep behaviors), Sleep Conflict (parent-child conflict at bedtime), Sleep Dependence (difficulty going to sleep without parent)-and a total score. Higher scores indicate more problematic bedtime interactions. Children's sleep problems and psychiatric symptoms at T1 and T2 were assessed with a clinical interview. PSIS scores were moderately stable from T1 to T2, and the factor structure of the PSIS remained relatively consistent over time. Higher total PSIS scores at T1 predicted increases in children's sleep problems at T2. Higher PSIS Sleep Conflict scores at T1 predicted increases in oppositional defiant disorder symptoms at T2. Children with more sleep problems and higher PSIS Sleep Reinforcement scores at T1 showed increases in attention deficit/hyperactivity disorder, depressive, and anxiety symptoms at T2. These findings provide evidence for the predictive validity of the PSIS and highlight the importance of early parent-child sleep interactions in the development of sleep and psychiatric symptoms in childhood. Parent-child sleep interactions may serve as a useful target for interventions.

A Developmental Cascade Model of Behavioral Sleep Problems and Emotional and Attentional Self-Regulation Across Early Childhood

This article documents the longitudinal and reciprocal relations among behavioral sleep problems and emotional and attentional self-regulation in a population sample of 4,109 children participating in Growing Up in Australia: The Longitudinal Study of Australian Children (LSAC)-Infant Cohort. Maternal reports of children's sleep problems and self-regulation were collected at five time-points from infancy to 8-9 years of age. Longitudinal structural equation modeling supported a developmental cascade model in which sleep problems have a persistent negative effect on emotional regulation, which in turn contributes to ongoing sleep problems and poorer attentional regulation in children over time. Findings suggest that sleep behaviors are a key target for interventions that aim to improve children's self-regulatory capacities.

Stability of sleep disorders from preschool to first grade and their bidirectional relationship with psychiatric symptoms

OBJECTIVES

To examine the prevalence and stability of DSM-4-defined sleep disorders from preschool to first grade and to explore the bidirectional relationship between sleep disorders and symptoms of psychiatric disorders.

METHOD

All children born in 2003 or 2004 in Trondheim, Norway, who attended regular community health checkups for 4-year-olds, were invited to participate (97.2% attendance; 82.0% consent rate, n = 2475) in this study. The authors recruited a screen-stratified subsample of 1250 children and interviewed 994 parents (79.6%) using a structured diagnostic interview (the Preschool Age Psychiatric Assessment). Two years later, 795 of the parents completed the interview.

RESULTS

There was stability in insomnia (adjusted odds ratio [OR] = 4.03, confidence interval [CI] = 2.83-5.75) and sleepwalking (adjusted OR = 19.28, CI = 4.53-82.10), whereas none of the children with hypersomnia or nightmare disorder at age 4 had the same disorder 2 years later. Insomnia increased the risk for developing symptoms of conduct disorder, major depressive disorder (MDD), and social phobia when the initial levels of insomnia were adjusted for. Symptoms of attention-deficit hyperactivity disorder, oppositional defiant disorder, and MDD at age 4 were statistically linked to insomnia at age 6. Sleepwalking predicted later separation anxiety disorder, whereas hypersomnia was unrelated to symptoms of psychiatric disorders.

CONCLUSION

Insomnia is a prevalent and stable disorder in children and is bidirectionally related to psychiatric symptoms.

Bedtime problems and night wakings in young children: an update of the evidence

Bedtime problems and night wakings in infants and young children are prevalent, persistent, and associated with a variety of impairments in youth and their families. Assessment strategies include clinical interview, sleep diaries, actigraphy, and subjective measures. A number of treatment approaches with varying degrees of empirical support are available, and several novel strategies have been evaluated in recent years. Appropriate sleep scheduling and a bedtime routine are important components of any treatment program.