Nocturnal wakefulness is normal during early infancy and usually decreases substantially over the first few months of life. Thus, the majority of children sleep through the night by 6 months of age [1]. Differentiating sleep problems from normal physiologic changes in development can be challenging for clinicians. Sleep problems are commonly referred to as “bedtime problems and night waking” in infants and young children and insomnia in older children and adolescents [2].

Insomnia affects both sleep duration and quality. Total mean sleep duration is 14.2 hours (standard deviation [SD], 1.9 hours) at 6 months of age versus a mean 8.1 hours (SD, 0.8 hours) at 16 years of age [3]. The American Academy of Sleep Medicine recommends the amount of sleep per 24 hours for pediatric populations to promote optimal health [4] (Table 1). Chronic insufficient sleep quantity and inadequate sleep quality can impact a child’s daytime functioning, causing daytime behavior problems, cognitive impairment, and mood disturbances [5]. Sleep problems in young children disrupt their parents’ sleep, affecting their mood and daytime functioning as well [6,7].

Chronic health problems (e.g., asthma, epilepsy, or atopic dermatitis) and developmental disorders will also adversely affect sleep [8]. This review describes behavioral insomnia of infants and young children and details its common interventions.

Considering its characteristic features, the International Classification of Sleep Disorders (ICSD) 2nd edition classified pediatric insomnia independently as “behavioral insomnia of childhood (BIC)” [9]. In the ICSD 3rd edition, pediatric insomnia was integrated into “chronic insomnia.” [9,10] Considering the distinctive characteristics of pediatric insomnia, the text mentions three subtypes of pediatric insomnia: (1) sleep-onset association type, a “child’s dependency on specific stimulation, objects, or setting for initiating sleep or returning sleep following an awakening; in the absence of these conditions, sleep-onset is significantly delayed;” (2) limit-setting type, “bedtime stalling or bedtime refusal that is met with and reinforced by inadequate limit-setting by a caregiver;” and (3) mixed type, “sleep-onset association difficulties and bedtime resistance.” [10]

Sleep associations are certain behaviors or environments that customarily appear at the time of sleep-onset that the child learns to need to fall asleep [5]. In the presence of a negative or inappropriate sleep-onset association, parental interventions (e.g., rocking, nursing, swinging) are required for the child to initiate sleep or return to sleep after a night awakening [5,9-11]. Therefore, frequent night awakenings are the presenting symptom of the sleep-onset association type [9,11].

The BIC limit-setting type, which usually begins after 2 years of age, occurs when the child refuses to go to bed [5,10]. Bedtime refusal and delaying tactics include attempts to delay bedtime (e.g., watching additional television) and the bedtime routine (e.g., requesting another story) or “curtain calls” after lights out (e.g., needing another story, hug, drink) [5,11]. It occurs when there are few or no limits instituted by parents around sleep behaviors (e.g., allowing the child to fall asleep while watching television or to play games until lights out) [11]. Parents may also institute limits in an inconsistent way (e.g., allowing the child to stay up late on weekends) [5,11].

Using a latent class analysis, Bruni et al. [12] recently suggested three pediatric insomnia subtypes and advocated different therapeutic approaches for each as follows: (1) presence of restless legs syndrome in dopaminergic dysfunction; (2) frequent depression and/or mood disorders in serotonergic dysfunction; and (3) common allergies and/or food intolerance in histaminergic dysfunction.

The prevalence of pediatric insomnia is reportedly 5%–20%, affecting up to 75% of children with neurodevelopmental comorbidities [13-15]. In Korea, a study of patients visiting secondary and primary pediatric outpatient clinics reported a 13.2% prevalence of pediatric insomnia in children and adolescents: 21% at age 0–1 year, 13% at age 2–5 years, 7% at age 6–12 years, and 6% at age 13–18 years [16]. Similar to the prevalence of general pediatric insomnia, bedtime problems and frequent night waking occur in 20%–30% of infants and young children [17].

The prevalence of sleep problems including insomnia may vary depending on cultural and regional factors [18,19]. Children from predominantly Asian (P-A) countries (China, Hong Kong, India, Japan, Korea, Malaysia, Philippines, Singapore, Thailand) had significantly increased parental perception of sleep problems than those from predominantly Caucasian (P-C) countries (Australia-New Zealand, Canada, United Kingdom, United States) (Table 2) [18].

Co-sleeping, broadly defined as room-sharing and bed-sharing, has generated a considerable amount of controversy. It is considered a factor that increases the chronic nature of sleep problems in P-C countries [11]. Co-sleeping is common in P-A countries, with no change across the preschool years [11,18,19]. However, when analyses of variance covarying with cosleeping were calculated that compared the predictors of sleep problems (night waking, sleep-onset latency, bedtime, nighttime sleep duration) between P-C and P-A countries, a significant difference was seen only in sleep-onset latency [18].

Many parents worry about the harmful effects of ignoring their child’s nighttime crying on their emotion and development. It is important to emphasize to parents that most behavioral sleep interventions involve some level of infant protest and that no published studies show such adverse effects [29]. Several randomized studies showed that behavioral sleep treatments do not lead to later emotional and behavioral problems or negative impacts on the parent-child relationship [25] at 5-year follow-up [39]. To the contrary, a longitudinal study showed that, in the condition of no sleep intervention, sleep problems (short sleep duration [≤10 hours], and frequent nocturnal awakenings [≥3 times]) at 18 months predicted a later incidence of emotional and behavioral problems at 5 years [40].

Behavioral treatments for young children result in significant improvements in sleep-onset latency and night waking without later causing emotional problems or negatively affecting the parent-child relationship. Parent education about a child’s sleep and sleep hygiene is essential for treatment. Teaching parents within busy clinic time is challenging. Consultation with a clinical psychologist or trained nurse practitioner is needed to educate and support parents in this area.