Waking up at night is biologically normal for toddlers, and most children between one and three years old do not consistently sleep through the night without at least occasional disruptions. The reasons range from an immature circadian clock and daytime nap patterns to medical irritants like reflux or eczema. Understanding why your toddler wakes up gives you a much better shot at figuring out which fixes are worth trying and which problems will resolve on their own.
Their Internal Clock Is Still Maturing
Adults have a roughly 24-hour internal clock that tells the body when to feel sleepy and when to wake. Toddlers have that clock too, but it runs on a slightly different schedule and is still catching up developmentally. Research on toddler melatonin timing shows that young children begin producing melatonin earlier in the evening than older kids or adults, a sign that the circadian system is not yet fully mature. That maturational lag means the signals telling your toddler’s brain when to stay asleep and when to transition between sleep cycles are not as reliable as they will eventually become.1PubMed Central. Circadian phase and its relationship to nighttime sleep in toddlers
This matters because sleep is not one long block of unconsciousness. Everyone cycles between lighter and deeper stages throughout the night, and at the boundary between cycles there is a brief moment of partial arousal. Adults barely notice these transitions. Toddlers, with their still-developing circadian system, are more likely to wake up fully during them and then struggle to fall back asleep without help.
How Daytime Naps Shape the Night
One of the most actionable factors you can adjust is your toddler’s nap schedule. A study of toddlers around 18 months found a strong negative relationship between nap length and nighttime sleep duration: longer naps predicted shorter nights and later bedtimes. Late-afternoon naps had the same effect, pushing sleep onset later and cutting into total nighttime sleep.2PubMed Central. Daytime nap controls toddlers’ nighttime sleep The researchers concluded that keeping naps moderate in length and starting them early in the afternoon led to longer nighttime sleep.
Napping also shifts a toddler’s internal clock. One study comparing toddlers who still napped with those who had dropped their nap found that nappers had melatonin onset about 38 minutes later in the evening, fell asleep nearly an hour later, and slept roughly 69 fewer minutes at night. Interestingly, total 24-hour sleep was similar between the two groups, meaning nappers were simply redistributing their sleep rather than getting less overall.3PLoS ONE. The Timing of the Circadian Clock and Sleep Differ between Napping and Non-Napping Toddlers
This does not mean you should abruptly eliminate naps. Most toddlers genuinely need daytime sleep until age three or beyond. But if your child is consistently fighting bedtime or waking frequently at night, experimenting with an earlier, shorter nap is one of the easiest interventions available.
Self-Soothing and How You Respond to Wakings
Here is a distinction that trips up a lot of parents: every toddler wakes at night, but not every toddler signals those wakings to you. The difference lies in whether a child can resettle independently. Research tracking infants from birth through 12 months identified three factors that predicted self-soothing at one year: spending less time being held or picked up out of the crib across the first year, having more quiet sleep at birth, and parents waiting a bit longer before responding to awakenings at three months.4PubMed Central. Nighttime sleep-wake patterns and self-soothing from birth to one year of age: a longitudinal intervention study
More recent work using motion sensors confirms the connection between parenting habits and self-soothing. Putting a child to bed drowsy but still awake, avoiding feeding as the primary strategy during night wakings, and using low-stimulation soothing (patting, shushing) rather than high-stimulation methods (picking up, rocking, bringing to another room) were all associated with more frequent episodes where the child woke and resettled without parental help.5PubMed. Sleep parenting practices are associated with infant self-soothing behaviors when measured using actigraphy
A large study of children at five months quantified the effect: the risk of sleeping fewer than six consecutive hours was about 2.6 times higher among children who were fed in response to every nighttime waking, and about 1.7 times higher in children who were rocked to sleep or brought into the parents’ bed, compared with children who were comforted in their own beds.6Archives of Pediatrics & Adolescent Medicine. Factors Associated With Fragmented Sleep at Night Across Early Childhood None of this means you are doing something wrong by comforting your child. It means the method you use shapes whether your toddler learns to bridge those normal between-cycle arousals alone.
Screens Before Bed
You have probably heard that screens and sleep do not mix. For toddlers, the evidence is concrete. When researchers measured what happened when young children used screens in the hour before bed, they found more parent-reported sleep problems, including bedtime resistance and signaled awakenings. Objective sleep measurements told the same story: screen use during the bedtime routine was linked to later sleep onset, shorter total sleep, and more variability in sleep timing from night to night.7PubMed Central. Screen use before bedtime: Consequences for nighttime sleep in young children The light from screens suppresses melatonin, and the stimulating content keeps a toddler’s brain in alert mode right when you want it winding down. This is one of the simplest things to eliminate from a bedtime routine if night waking is a problem.
Teething, Illness, and Other Temporary Disruptions
Some night waking is just a phase tied to something physical and temporary. Teething is the classic example. A meta-analysis pooling data from over 3,500 children found that about 70% showed some signs or symptoms during primary tooth eruption, with gum irritation, irritability, and drooling being the most common. Teething can raise body temperature slightly, though not enough to count as a true fever.8Pediatrics. Signs and Symptoms of Primary Tooth Eruption: A Meta-analysis The discomfort is real but short-lived, usually lasting a few days per tooth. If your toddler’s sleep suddenly falls apart for a few nights and you can see swollen gums, teething is a likely culprit, and it will pass.
Motor milestones cause similar transient sleep disruptions. Research on infants who began pulling to stand found that among early achievers of this milestone, the new skill was directly linked to a period of disrupted sleep.9PubMed. Sleep disruption and motor development: Does pulling-to-stand impacts sleep-wake regulation? Many parents recognize this pattern: the toddler who learns to climb out of the crib, or starts walking, suddenly sleeps terribly for a week. The brain appears to “practice” new motor skills during sleep, and the excitement or frustration of the new ability can wake a child up. These regressions tend to resolve once the skill is consolidated.
Medical Causes That Are Easy to Miss
When night waking is severe and persistent, it is worth considering whether something medical is going on. Several conditions disrupt toddler sleep in ways that look like ordinary night waking but respond to treatment.
Reflux
Gastroesophageal reflux causes stomach acid to travel back up the esophagus, and it can be especially disruptive at night when a child is lying flat. A study comparing sleep in infants with reflux to population norms found dramatically higher rates of night waking: 50% of reflux babies aged 3 to 12 months woke more than three times per night versus 13% of healthy controls, and among toddlers aged 12 to 24 months the gap widened to 60% versus 10%. Children with reflux also reached the milestone of sleeping through the night significantly later.10PubMed. The sleep patterns of infants and young children with gastro-oesophageal reflux Separate research confirmed that the onset of a reflux episode during sleep is associated with significantly more sleep-stage changes compared to reflux-free periods, meaning even subclinical reflux can fragment a child’s sleep architecture.11PubMed Central. Change of Sleep Stage during Gastroesophageal Reflux in Infants Signs to watch for include arching the back during or after feeding, frequent spitting up, and discomfort when lying down.
Eczema and Skin Conditions
Atopic dermatitis (eczema) is one of the most common chronic conditions in young children, and its impact on sleep is substantial. Itching from eczema tends to worsen at night, and scratching movements repeatedly pull children out of sleep.12Journal of Allergy and Clinical Immunology. Sleep disorders and atopic dermatitis: A 2-way street? A survey of preschoolers with eczema found sleep disturbance on 86% of nights during flares, with an average of 2.7 wakings per night.13PubMed. Sleep difficulties and their management in preschoolers with atopic eczema A scoping review cataloging the range of sleep problems found that eczema drives both loss of sleep (more wakings, delayed sleep onset, less total sleep) and unusual behaviors during sleep, including restlessness, limb movements, and excessive sweating.14PubMed Central. Sleep Disturbances in Children With Atopic Dermatitis: A Scoping Review If your toddler’s skin is dry, red, or rough, treating the eczema itself often improves sleep more than any bedtime routine change could.
Iron Deficiency
This one flies under the radar. Iron deficiency, even without full-blown anemia, can cause restless sleep, bedtime resistance, and daytime sleepiness in toddlers. A case report described a two-year-old whose sleep problems resolved after iron infusion, highlighting that clinicians should consider checking iron status even when standard blood counts look normal.15PubMed Central. Terrible twos: intravenous iron ameliorates a toddler’s iron deficiency and sleep disturbance More concerning, research on infants with iron-deficiency anemia found that their sleep alterations persisted years after the anemia was corrected, suggesting that prolonged iron deficiency during a critical developmental window can leave a lasting mark on sleep architecture.16PubMed Central. Sleep alterations and iron deficiency anemia in infancy Toddlers who are picky eaters, drink large amounts of cow’s milk (which impairs iron absorption), or were born premature are at higher risk.
Obstructive Sleep Apnea
Enlarged tonsils and adenoids are the most common cause of obstructive sleep apnea in children. Unlike adult sleep apnea, which presents as snoring and daytime drowsiness, toddler sleep apnea can look like agitated sleep with frequent position changes, excessive sweating, or sleeping in unusual postures like a hyperextended neck.17PubMed Central. Obstructive sleep apnea syndrome in children: Epidemiology, pathophysiology, diagnosis and sequelae If your toddler snores loudly, pauses in breathing, or sleeps in odd positions, it is worth bringing up with your pediatrician.
Sensory Processing and Temperament
Some toddlers simply have a harder time tuning out the world. Research comparing toddlers with sleep problems to those without found that the sleep-problem group showed atypical sensory responses across multiple patterns: low registration (seeming unaware of stimuli), sensory sensitivity (getting easily overstimulated), and sensory avoiding (actively pulling away from sensory input).18PubMed. Sensory processing in typically developing toddlers with and without sleep problems A separate study found that increased sensory sensitivity correlated with taking longer to settle to sleep, while increased sensory seeking correlated with shorter daytime naps.19PubMed. Sensory Processing and Sleep in Typically Developing Infants and Toddlers
In practical terms, the toddler who notices every sound, every texture on the sheets, every shadow on the ceiling is the same toddler who takes forty-five minutes to fall asleep and wakes at every creak of the house. Reducing sensory input at bedtime (dimmer lights, white noise, consistent textures) can help, but it is also worth recognizing that some of this is temperamental. A “difficult” temperament was identified in the fragmented-sleep research as an independent risk factor for poor sleep at five months, separate from anything parents were doing.6Archives of Pediatrics & Adolescent Medicine. Factors Associated With Fragmented Sleep at Night Across Early Childhood You may be doing everything right and still have a child whose wiring makes consolidated sleep harder to achieve.
Does Sleep Training Cause Harm?
This is one of the most emotionally charged questions in early parenting. A randomized controlled trial compared two common behavioral sleep interventions (graduated extinction, where you wait increasingly longer intervals before responding, and bedtime fading, where you temporarily push bedtime later to match when the child naturally falls asleep) against a control group. Both methods led to children falling asleep faster and waking less. Crucially, cortisol levels actually showed small-to-moderate declines in the intervention groups compared to controls, and at the 12-month follow-up there were no differences in emotional or behavioral problems, and no differences in attachment security between the groups.20Pediatrics. Behavioral Interventions for Infant Sleep Problems: A Randomized Controlled Trial
This does not mean sleep training is mandatory or right for every family. But the fear that letting a child cry for measured intervals damages the parent-child bond does not hold up in the evidence. For families who choose this path, the data is reassuring. A related finding from attachment research is also worth noting: when actual objective sleep recordings were compared with mothers’ reports of sleep problems, objective sleep was not associated with attachment security. Mothers’ perceptions of sleep problems, however, were associated with the child’s dependency, suggesting that what feels like a sleep problem sometimes reflects the emotional dynamics of the relationship rather than a true sleep disorder.21Infant Behavior and Development. Is attachment security related to sleep–wake regulation?: Mothers’ reports and objective sleep recordings
The Toll on Parents
Toddler sleep problems do not stay in the toddler’s room. Research has consistently found that night waking is linked to maternal and paternal stress, with the number of awakenings and the time the child takes to fall asleep both predicting higher parental distress.22PubMed Central. Predictive Factors of Toddlers’ Sleep and Parental Stress The relationship appears to be bidirectional. One study found that parent insomnia rates were roughly double when their child had a sleep disorder, even after adjusting for other variables.23PubMed Central. Relating Parental Stress with Sleep Disorders in Parents and Children
Co-sleeping complicates the picture. Research on toddler sleep problems and maternal mental health found that shorter maternal sleep mediated the link between perceived toddler sleep problems and symptoms of depression, anxiety, and stress, but this pathway was only significant among mothers who co-slept.24PubMed Central. Perceived Toddler Sleep Problems, Co-sleeping, and Maternal Sleep and Mental Health Co-sleeping parents are, by definition, more exposed to every waking, which may intensify both the perception of the problem and its mental health impact. If you are co-sleeping and struggling, this does not mean you must stop, but it is worth being honest about whether the arrangement is working for everyone in the bed.
When Night Waking Persists
Most toddler sleep disruptions resolve. But when they do not, the downstream effects are real. A large longitudinal study found that sleeping 10 hours or less per night at 18 months and frequent nighttime awakenings both predicted higher rates of emotional and behavioral problems later in childhood. The effect followed a dose-response pattern: more awakenings meant higher risk, and the association held even after adjusting for a wide range of confounders. Three or more awakenings per night at 18 months predicted roughly 1.2 to 1.9 times the risk of later behavioral difficulties depending on the specific type of problem measured.25JAMA Pediatrics. Later Emotional and Behavioral Problems Associated With Sleep Problems in Toddlers: A Longitudinal Study
This should be taken seriously but kept in perspective. A risk ratio of 1.5 means the risk goes up, not that problems are inevitable. And the same study found that the association held across a range of sleep durations, suggesting there is no single magic number of hours that guarantees good outcomes. The important takeaway is that persistent, severe sleep disruption in the toddler years is worth addressing rather than simply waiting out, particularly when it co-occurs with daytime behavioral concerns.
The Evolutionary Angle
It is easy to feel like your toddler’s sleep is broken when everyone around you seems to have a child who sleeps twelve uninterrupted hours. But a growing body of scholarship argues that solitary, consolidated infant sleep is a historically recent expectation, not a biological norm. For most of human history, infants and toddlers slept in close contact with caregivers, waking and feeding throughout the night.26PubMed. Sleep Consolidation, Sleep Problems, and Co-Sleeping: Rethinking Normal Infant Sleep as Species-Typical From this perspective, frequent night waking is not a problem to be solved but a feature of how human infant brains developed over hundreds of thousands of years. The mismatch between what toddler brains are wired for and what modern Western sleep culture expects of them explains a lot of the anxiety parents feel. Your toddler may be doing exactly what toddlers have always done. Whether that is acceptable depends on how much it is affecting your family’s functioning, not on whether it matches an idealized norm.
Separation Anxiety and Emotional Regulation
Bedtime is one of the first daily separations a toddler faces, and for some children it is genuinely distressing. Research on toddlers in foster care found that an attachment-focused intervention reduced sleep problems, and the improvement was mediated by a reduction in separation distress. In other words, when the children felt less anxious about being apart from their caregiver, they slept better.27Children and Youth Services Review. Randomized trial of Promoting First Relationships: Effects on maltreated toddlers’ separation distress and sleep regulation after reunification While this study involved a specific vulnerable population, the underlying mechanism applies broadly. A toddler who experiences bedtime as a threatening separation is going to fight it, and once asleep, any between-cycle arousal brings the anxiety flooding back.
Predictable, warm bedtime routines function partly as a buffer against this anxiety. When a child knows exactly what will happen (bath, book, song, lights out) and trusts that the caregiver will be there in the morning, the emotional cost of falling asleep decreases. Sudden changes to routine, a new sibling, a parent traveling, or a move to a new house can spike separation anxiety and temporarily destroy sleep gains you thought were locked in. These setbacks are normal and usually temporary once the child adjusts to the new normal.