Sleep Health

Sleep Regression 101: Exploring the reasons behind sleep disturbances in infants and toddlers

June 20, 2023
Cecelia Beringer

Sleep regression is a phenomenon characterized by a temporary disruption of sleep patterns and behaviors in babies and toddlers, which can result in sleep disturbances for both the child and their caregivers.

This disruption usually occurs during critical development periods, like when a child is transitioning from one developmental stage to another. Understanding the factors that contribute to sleep disturbances is essential to effectively manage sleep regression.

Recent research has identified several biological, psychological, and environmental factors that influence sleep in young children, including factors such as the child’s cognitive development, sleep environment, and parenting behaviors.

Given the importance of sleep for a child’s healthy growth and development, understanding the factors contributing to sleep disturbances during developmental transitions is critical for parents, caregivers, and healthcare professionals.

Stages of Sleep Regression

There are several stages of sleep regression that parents should be aware of. These stages are often associated with specific sleep regression ages or developmental milestones.

Newborn Sleep Regression

Newborns typically sleep 16 to 17 hours daily, but their sleep patterns are irregular. Newborn sleep regression can occur  at around 4 months of age when babies begin to develop more regular sleep patterns. During this period, babies may wake more frequently at night or have difficulty settling down to sleep.

4 Month Sleep Regression

The 4 month sleep regression is a significant milestone in a baby’s sleep development. It occurs when a baby’s sleep cycle matures, and they transition from a newborn’s irregular sleep patterns to more adult-like sleep cycles. During this period a baby may experience more frequent wake-ups during the night and resist falling asleep, leading to sleep deprivation for both the baby and the parents.

6 Month Sleep Regression

The 6 month sleep regression is another common period of disrupted sleep. At this age, babies become more aware of their surroundings and may become more easily distracted during nap time or bedtime. They may also develop separation anxiety and trouble falling asleep without a parent or caregiver.

8 Month Sleep Regression

The 8 month sleep regression is another critical phase in a baby's sleep development. It often coincides with major milestones such as crawling, pulling up, and teething, which can lead to disrupted sleep. Babies at this age may wake up more frequently during the night and resist going back to sleep.

10 Month Sleep Regression

The 10 month sleep regression is the last significant sleep regression that babies typically experience. At this age, babies may start to experience nightmares, which can cause them to wake up crying and frightened during the night. They may also experience separation anxiety and have trouble falling asleep without a parent or caregiver present.

12 Month Sleep Regression

At around 12 months of age, babies may experience another period of sleep regression. This is thought to be due to the transition from just two naps a day to one nap a day. During this period, babies may have difficulty falling asleep at night or may wake up earlier in the morning.

Two Year Sleep Regression

Around two years of age, toddlers may experience another period of sleep regression. This is thought to be related to their increased independence and desire for control. During this period, toddlers may have difficulty settling down to sleep or may wake up frequently during the night.

Sleep Cycles and Stages

Infants and toddlers have distinct sleep cycles and stages crucial for their development. The two main sleep stages are rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Infants spend more time in REM sleep, which is essential for brain development, while toddlers spend more time in NREM sleep, which is important for physical growth (Bathory & Tomopoulos, 2017).

Total Sleep Time

Infants typically require around 14-17 hours of sleep per day, while toddlers need about 11-14 hours per day, including naps (Mindell & Williamson, 2018). However, these estimates can vary depending on the child's needs and age.

Wakefulness and Naps

Infants and toddlers experience periodic awakenings at night, with the frequency decreasing as they age (Galland & Taylor, 2016). Napping is also essential to a child's sleep pattern, with infants taking multiple naps throughout the day and toddlers transitioning to one nap daily (Bathory & Tomopoulos, 2017).

Changes in Sleep Patterns During Developmental Milestones

During the early stages of life, infants and toddlers experience significant developmental changes that impact their sleep patterns. This section explores how teething, growth spurts, and cognitive leaps can cause changes in sleep routine and quality.


Teething can cause discomfort and pain, leading to changes in sleep patterns. Infants may wake up more frequently during the night or have trouble falling asleep (Santana-Mora et al., 2019).

Growth Spurts

During growth spurts, infants may require more frequent feedings and experience increased hunger, leading to changes in sleep patterns(Friedman & Zeichner, 2017).

Cognitive Leaps

Cognitive leaps, or significant advances in cognitive development, can impact sleep patterns. During these periods, infants and toddlers may experience changes in their  sleep routine.

The Impact of Developmental Changes on Sleep Quality and Duration

Developmental changes can significantly impact the quality and duration of sleep in infants and toddlers, leading to sleep fragmentation, night wakings, and early wake ups.

Sleep Fragmentation

Sleep fragmentation is when infants and toddlers wake up multiple times. This results in reduced total sleep time and decreased sleep quality.

Night Wakings

Night wakings can be common during developmental milestones, which leads to disrupted sleep patterns for the child and caregiver. It is important to address these disturbances to ensure proper sleep for both parties (Santana-Mora et al., 2019).

Early Wake-Ups

Developmental changes can also result in early-wake-ups, where infants and toddlers wake up earlier than usual. This can impact the child’s mood and behavior throughout the day and may require adjustments to their sleep routine (Friedman & Zeichner, 2017).

Regulation of Sleep in Infants and Toddlers

The neurobiological mechanisms involved in sleep regulation differ between infants and adults(Mirmiran et al., 2003). Infants have shorter sleep cycles,  with a higher proportion of REM sleep compared to NREM(Mirmiran et al., 2003).

As they age, the proportion of NREM sleep increases, and the frequency of REM sleep decreases. The maturation of the suprachiasmatic nucleus and other brain regions involved in sleep regulation contributes to these changes.  

Role of Neurotransmitters in Sleep Regulation and Disturbances

According to Frank (2017), neurotransmitters such as serotonin, dopamine, and acetylcholine play important roles in sleep regulation. Serotonin aids NREM sleep, while dopamine promotes wakefulness. Acetylcholine is involved in REM and NREM sleep, with higher levels during REM sleep. Imbalances in these neurotransmitters can lead to sleep disturbances such as insomnia, narcolepsy, and restless leg syndrome.

Role of Hormones in Sleep Regulation and Disturbances

Researchers have evaluated that sleep is regulated by cortisol, melatonin, and growth hormone (Frank, 2017). Cortisol levels are the highest in the morning and gradually decrease throughout the day, causing people to feel more awake. On the other hand, melatonin is secreted at night and causes sleepiness. Growth hormone is essential for physical growth and is primarily secreted during deep sleep. Hormonal imbalances can lead to sleep disorders such as insomnia, sleep apnea, and hypersomnia.

Factors Affecting Sleep Quality

Sleep quality in infants and toddlers is crucial for their growth and development. A good sleep environment is essential for healthy sleep patterns, and factors such as light, noise, and temperature can significantly affect sleep quality.

Impact of Light on Sleep Quality

Light exposure during the night has been shown to delay the onset of sleep, reduce the total amount of sleep, and increase the number of night awakenings in infants and toddlers(Mindell, Sadeh, Wiegand, How, & Goh, 2010). Research has also found that using electronic devices emitting blue light can negatively impact sleep quality in children(Cheung et al., 2017).

Impact of Noise on Sleep Quality

Research has shown that infants are more sensitive to noise than adults. Noise can interfere with sleep initiation and cause night awakenings, leading to sleep fragmentation(repetitive, short interruptions during sleep), and reduced sleep quality.

Impact of Temperature on Sleep Quality  

Temperature is another essential factor in creating an ideal sleep environment for infants and toddlers. Infants and toddlers are more sensitive to temperature changes and require a comfortable sleep environment. Studies have shown that a temperature between 65-70°F(18-21°C) is optimal for a good sleep environment.

Impact of Parenting Practices

Parenting practices are vital in determining sleep quality in infants and toddlers. Practices such as co-sleeping, bedtime routines, and feeding schedules can impact sleep quality. Research has shown that co-sleeping can lead  to sleep disturbances and impair sleep quality(Mindell, Sadeh, Kohyama, & How, 2010). On the other hand, bedtime routines and feeding schedules can promote better sleep quality in infants and toddlers(Mindell, Telofski, Weigand, & Kurtz, 2009).

The Role of Behavioral Factors in Sleep Disturbances

Behavioral factors such as bedtime routines and sleep associations can significantly impact sleep quality in infants and toddlers.

Bedtime Routines

Establishing a regular bedtime routine can help infants and toddlers develop healthy sleep habits. A consistent routine that includes bath time, storytime, and soothing music can signal to a child that it’s time to sleep and help them feel more relaxed and comfortable(Mindell & Williamson, 2018).

Sleep Associations

Sleep associations refer to the habits or objects a child associates with falling asleep, such as a favorite blanket or being rocked to sleep. While sleep associations can be comforting, they can be problematic if the child becomes over-reliant on them to fall asleep. Gradually reducing reliance on sleep associations can help infants and toddlers learn to self-soothe and fall asleep independently(Mindell & Williamson, 2018).

Parenting Styles

Different parenting styles can have an impact on sleep quality. For example, authoritarian parenting, which emphasizes strict rules and punishments, can increase stress in a child, negatively impacting sleep(Jiang et al., 2019). On the other hand, authoritative parenting , which emphasizes warmth and support, can promote healthy sleep habits and reduce sleep disturbances(Jiang et al., 2019).

Sleep Training Methods

Sleep training refers to the methods parents can use to help their child learn to fall asleep independently. Common sleep training methods include gradual extinction, in which parents gradually reduce the amount of time spent soothing the child to sleep. There is the Ferber method, which involves gradually increasing the time the child is left alone in the crib. While sleep training can effectively improve sleep quality, there is an ongoing debate about the potential negative effects of these methods on infant-parent attachment(Price et al., 2021).

Strategies For Creating a Sleep-Conductive Environment

Here are the strategies for creating a sleep-conducive environment for babies and toddlers:

  • Establishing consistent bedtime routines that promote relaxation and winding down before sleep
  • Using white noise or other sounds to create a calming sleep environment and mask disruptive noises
  • Maintaining a comfortable sleep environment with appropriate room temperature and bedding
  • Ensuring the sleep environment is dark and free of stimulating visual stimuli
  • Minimizing exposure to electronic devices before bedtime
  • Encouraging daytime physical activity and exposure to natural light to promote healthy sleep-wake cycles
  • Establishing consistent sleep associations, to promote feelings of comfort and security during sleep


Sleep Regression in infants and toddlers is a complex phenomenon caused by various factors. This review has explored the mechanisms and factors contributing to sleep disturbances in babies and toddlers. Research has shown that developmental changes, environmental factors, and behavioral factors can all affect sleep quality in infants and toddlers. It is important that parents and caregivers be patient and understand that sleep regression is a normal part of development and will eventually pass. If sleep disturbances persist or are severe, parents and caregivers should seek advice from a healthcare provider.

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