15 Month Sleep Regression: Why It Happens and How to Get Through It

Babies and toddlers go through several sleep regressions during the first two years. Just when you thought your baby would sleep through the night and take great naps, another sleep regression seems to hit. During one of these exhausting time periods, your baby will wake frequently at night, wake too early for the day, and/or take short naps. In this post, I’ll discuss the 15 month sleep regression, explain why it happens, and give you tips to get through it based on over years’ experience as a sleep consultant.

What is a Sleep Regression?

During a sleep regression that lasts an average of 3 to 6 weeks, a baby or toddler who was sleeping fine suddenly starts waking at night, taking short naps, and/or skipping naps for no apparent reason. Typically, these time periods start without warning and leave parents exhausted and confused. The good news is that it means your baby is developing properly and if you handle them properly, they don’t have to last forever. Sleep regressions happen around 4 months old, 6 months old, 8 to 10 months old, 11-12 months, 15 months, 18 months, and 2 years old.

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15 Month Sleep Regression: How Is It Different?

Most sleep regressions happen during developmental milestones. However, the 15-month sleep regression isn’t a change in how a baby sleeps like the 4-month sleep regresson. And, although some toddlers start walking around this age, it’s not as much tied to developmental milestones as the 8-10 month sleep regression.

At 15 months old, this regression typically occurs because your toddler is likely changing their schedule. This is especially true if they’ve already been walking for a while. My older son started walking around 11 months old, for example. When a toddler first starts walking, it can be exhausting. But, once they’re up and running (literally!), their schedule often changes.

How to Get Through the 15 Month Sleep Regression

If your toddler is struggling with the 15-month sleep regression, there are a few ways to get through it. Here are my tips:

  • Increase Wake Windows – If you’re still using a typical 12-month old schedule, consider increasing your baby’s wake windows to 3 1/2 to 4 hours. Although it might feel like there’s not much different month-to-month, schedules can change quickly. Check out our toddler schedules by month here. Also, keep in mind if your toddler is still taking two naps, nighttime sleep could decrease down to 10 to 10 1/2 hours. But, that doesn’t mean it’s a bad schedule. You might simply need to shift it forward by an hour or so.
  • Increase Solid Food – Active toddlers who are also growing at lightning speeds have very fast metabolisms. I know many of us worry about healthy weights for our children but keep in mind that it can feel like your toddler is eating more than you are on a regular basis! Be sure to offer three solid meals plus 2-3 snacks AND 16-20 oz of milk a day. Your toddler will indicate when they are done with their meal by signaling or refusing to eat. Toddlers also tend to graze a lot. You’d be surprised how often we figure out a toddler is hungry at night and that’s why they are waking up!
  • Promote Independent Play – Separation anxiety has peaks and valleys throughout childhood so if your toddler is exhibiting uneasiness, be sure to promote independent play throughout the day. If you are only separating from your toddler at night, this can have negative consequences. Try leaving the room during the day for short durations so you can show them you always come back.
  • Transition to One Nap – If your toddler is already awake 3 1/2 to 4 hours between naps and waking frequently at night or for a long period of time in the middle of the night, it might be time to transition to one nap altogether. Transitioning from two naps to one nap can be bumpy but within 2-3 weeks, your toddler should be sleeping much better at night.

Can I Do Sleep Training?

What about sleep training? Keep in mind that sleep training is NOT the answer to every sleep problem! There are many reasons babies and toddlers wake up at night. If you do sleep training such as Ferber or Cry It Out, you run the risk of having long periods of crying without success.

However, if your baby or toddler has always been a troubled sleeper, adding sleep training into the above-mentioned tips can help your child sleep through the night.

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How Long Does the 4 Month Sleep Regression Last? And, How to Shorten It

How Long Does the 4-Month Sleep Regression Last?The 4-month sleep regression is an exhausting time in a family’s life. Your baby might be waking every 1-2 hours all night and taking short naps. And, if your baby is going through this, you’re probably asking yourself how long the 4-month sleep regression lasts. Based on my 10+ years as a sleep consultant, it doesn’t have to be as long as you think. In this blog post, I’ll share tips to get through the 4-month sleep regression.

What Is the 4-Month Sleep Regression?

The 4-month sleep regression marks the time when your baby stops sleeping like a newborn and starts sleeping more like an adult. Newborns spend a lot of time in deep sleep which is why they can sleep through so much in those early days. Once they go through this period of development, they change their sleep cycles which means they are sometimes only in light sleep and will wake more easily. So, the 4-month sleep regression is only the name we give this period of development. Do all babies go through the 4-month sleep regression? Yes, all babies go through this change and there isn’t a way to stop it. It’s actually a good sign your baby is developing appropriately!

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The most common signs of the 4-month sleep regression usually include one or more of the following:

  • Waking a lot at night (even when they used to sleep in long stretches) – waking every 1-2 hours at night is common.
  • Taking short naps of 20-30 minutes, sometimes 45 minutes.
  • Can’t be put down awake (or even asleep sometimes!) Baby wants to sleep only in your arms or a carrier/sling.
  • Irritability and Fussiness (though that can be simply due to sleep deprivation!)
  • Needing to be put back to sleep the same way each time (e.g. rocking or feeding back to sleep).

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How Long Does 4 Month Sleep Regression Last?

The 4-month sleep regression starts around 3 to 4 months old and lasts around 3-4 weeks at its peak. But since it’s a permanent change to how your baby sleeps, it doesn’t ever “end” in a traditional sense. Some babies will begin (or go back) sleeping fine again. But, others will continue to wake up frequently at night and take short naps. Over the past 10+ years, I’ve gotten phone calls or e-mails from parents of 4-month olds, 6-month olds, 10-month olds, 12-month olds, or 18-month olds with virtually the same exact sleep problems: frequent night-waking and/or short naps.

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How to Shorten This Regression

The only way to “end” the sleep problems this regression causes is to help your baby sleep better with their new sleep cycles. If you don’t want this regression to last months when it can last just a few weeks, you need to help your baby learn to put sleep cycles together.

Linking sleep cycles sounds simple enough when you’re an adult but for babies, it can be difficult. The most common reasons babies struggle moving into the next sleep cycle is due to hunger and sleep associations. A sleep association is a way in which your baby falls asleep. Because this is how they fall asleep, this is how they expect to fall BACK to sleep. Examples of sleep associations include rocking, feeding, bouncing, sucking on a pacifier, and driving in a car.

So, the key to shortening the 4-month sleep regression is simply to have your baby fall asleep the same way they will need to put themselves back to sleep. We typically do this by teaching babies to self-soothe with gentle sleep training. There are many methods to do sleep training or sleep coaching. The key is to find the one that works best for your baby’s temperament and personality. Please poke around and read through our many blog posts about this topic and more!

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Baby Insomnia or Split Night: Why It Happens and How to Fix

Baby insomnia is when your baby is awake in the middle of the night for 2-3 hours at a time. It is sometimes called a “split night” and usually lasts for weeks or months. This post will explain why baby insomnia happens and ways you can fix the problem based on my 10+ years as a sleep consultant.

What Is Baby Insomnia or a Split Night?

Insomnia is usually defined as the inability to sleep when you are actively trying to sleep. This could mean that it’s hard to fall asleep, hard to stay asleep, awake for long periods at night, or wake up too early in the morning.

Baby insomnia is the same but sometimes occurs when there is a mismatch between how much sleep a parent thinks their baby needs and how much sleep their baby actually needs.

When a parent comes to us with a case of baby insomnia, it usually means the baby is awake for long periods in the middle of the night (2+ hours) and can’t go back to sleep. When a baby is taking too long to fall asleep at night or waking up too early, we don’t typically call that “insomnia.” Same for a toddler stalling.

In most cases, if your baby is awake at night but happy and not crying, this is a good indication they have insomnia.

If your baby is crying when they are alone but awake and happy when you’re holding them, that can also be insomnia for a social child. After all, tossing and turning alone isn’t fun for anyone when you can’t sleep!

This is often called a “split night” because your baby might sleep a long stretch at the beginning of the night, wake up for 1-3 hours, then finish their nighttime sleep. They are “splitting” the night into two long fragments.

What About When Baby Falls Asleep In Your Arms But Wakes Up When Put Down?

If your baby is falling asleep in your arms but waking up when you put them in their crib, we would NOT consider that insomnia. If your baby will only sleep in your arms or on your chest, this is usually a case of sleep associations not insomnia.

Why Is Insomnia Bad?

The reason this is an issue is it’s not as restorative for your baby’s sleep, in general, and can cause problems with their schedule. It can also cause your child not to get enough sleep in a 24-hour period. And, just like adults, they can feel tired during the day.

So, why does insomnia happen in babies?

Top 5 Reasons for Baby Insomnia

There are 5 primary reasons for long night-waking in children:

  • Developmental Milestones and Sleep Regressions – The most notable reason your baby might wake up for long periods at night is that they are working on a new skill or developmental milestone. When our minds are very busy, we have trouble sleeping (obviously). For adults, it’s often due to something about which we’re stressed or worried. For babies, it might be a new skill they’re learning. During some developmental periods, you’ll also notice a sleep regression, a period of time when your baby starts waking a lot for no apparent reason.
  • Scheduling Problems – Besides developmental leaps, a scheduling problem is the most common reason for insomnia. But, it can be complicated how to fix it which I will explain below.
  • Medication Side Effects – Although it’s rarer, there are occasionally children on medications that have a side effect of insomnia.
  • Allergies and Milk Intolerance – In a small number of cases, milk intolerance is to blame for sleeplessness and other allergies.
  • Sensory Processing Disorder – Sensory Processing Disorder (SPD) can also cause insomnia in babies and toddlers. This was the case for one of my clients with a 2-year-old at the time. He would wake up for 1 to 3 hours every single night. In the end, a weighted blanket was the only thing that helped. SPD makes it difficult for children to process information from their senses and then respond appropriately. Typically, one or more senses over- or under-react so it isn’t difficult to see how that could impact sleep.

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What About Teething and Illness?

Teething and illness can both cause discomfort and thus, sleeplessness. However, this is typically short-lived. And, by the time you are wondering if your baby has insomnia, it’s usually over. Therefore, I didn’t include them in the list. Babies get teeth on and off for 2+ years. If they have night-waking related to teething, it’s usually when the tooth is cutting through the gums and then it’s over. That typically takes 3-5 days per tooth. In some cases, they might get two at the same time or back-to-back but even then, it will typically last two weeks or less of sleeplessness (with some nights being better than others.) Insomnia typically lasts several weeks or months.

Ways to Fix Your Baby’s Insomnia

For the purposes of this article, we will be sharing how to fix insomnia when it’s a scheduling problem. For any potential medical or development issues, please see your medical provider.

If your baby has had insomnia for weeks or months, you probably want to fix it. I say “probably” because in some cases, a split night isn’t the worst thing in the world. If your baby is happy and thriving, it may be a phase they go through until they are ready for their next schedule, for example. If it’s keeping you up at night, consider changing your own sleep environment to combat it rather than changing theirs.

However, if your baby seems exhausted during the day and/or is not thriving, you should definitely address the issue. But, how do you fix insomnia?

If it’s due to a sleep regression, you typically need to ride it out. Although there are sleep regressions at various ages, we find that insomnia occurs most during the 8 to 10-month sleep regression and during the 18-month sleep regression in our experience. During other sleep regressions, we notice frequent night-waking but not necessarily long periods of non-sleeping.

When insomnia is due to a scheduling problem, thankfully, there are things you can do to fix it! Unfortunately, it can be one of the most challenging sleep problems to fix. Here are a few tips:

  • Too Much Daytime Sleep – This is probably the easiest scheduling problem to solve. If your baby is older than 6 months old and napping longer than 2 1/2 to 3 hours during the day, we typically need to reduce the amount of daytime sleep. Note: You don’t have to reduce it if there isn’t insomnia. This is only if it’s causing an issue at night. When your baby is sleeping too much during the day, they might not be sleepy enough at night to stay asleep. They might fall asleep fine at bedtime (or not), but they simply can’t stay asleep.
  • Bedtime Is Too Early – You might know about wake windows so you put the baby to bed at night after their appropriate wake window. Great! Only sometimes this can cause split nights. For example, your baby naps from 2 to 3 PM and can stay awake 3 hours. So, you put them to bed at 6:00 PM. Unfortunately, this can cause split nights because while early bedtimes are good, your baby’s internal clock might be set for “nighttime sleep” from 7:00 PM to 7:00 AM, for example. If their bedtime is too early, they treat bedtime more like a long nap than bedtime. This happens to adults, too. We see this to happen to babies most when they are transitioning from two naps to one nap
  • Too Long In Bed Problem – Similar to bedtime being too early, another issue is what Dr. Ferber calls the “Too Long In Bed Problem.” Essentially, you have your baby in bed for more hours than they are capable of sleeping. If this is the case, you need to try to have your baby in bed for just the right amount of hours. The worst thing you can do in a case like this is let your baby “sleep in!” The amount of sleep in a 24-hour period will stay relatively constant. If your baby needs 13 hours of sleep a day, naps for 3 hours, and is in bed for 12 hours, they will likely be awake for two hours in that 12-hour period whether it’s at the beginning, the end (early waking), or in the middle (split nights.) To fix this issue, “squeeze” the sleep together by setting an appropriate schedule with only the number of hours of sleep your baby needs.
  • Overtiredness – Overtiredness can be terrible for your baby’s sleep but usually, it causes frequent night-waking, not insomnia. In some cases, though, it can cause insomnia. Our bodies release hormones (cortisol) to fight fatigue and give us a “second wind.” If we go to bed overtired, we might wake up restless and unable to sleep. In my experience, babies who have insomnia due to this reason are fussier at night than for the above reasons. They are quite miserably tired.


As I mentioned, insomnia is one of the most challenging sleep problems we face as parents and as sleep consultants. Although it should feel simple to put your baby to sleep when they’re tired, there is a bit of an art form to it. When we work directly with families, we typically keep a sleep log while fine-tuning the schedule so we can accurately see the primary cause of insomnia. If you try to solve the wrong problem, you can make sleep even worse! Give a few things a try for 2-3 days and then make more adjustments. If you get stuck, feel free to reach out to us!

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Solve Your Child’s Sleep Problems by Dr. Richard Ferber

The post Baby Insomnia or Split Night: Why It Happens and How to Fix appeared first on The Baby Sleep Site – Baby / Toddler Sleep Consultants.


Baby Sleep Cycles By Age Chart

Understanding how your baby sleeps can help you get your baby to sleep through the night, take better naps, thrive, and be happier! Part of understanding how babies sleep is understanding how their sleep cycles work. This post will explain baby sleep cycles by age and provide a chart for guidance based on my 10+ years as a sleep consultant.

What is a Sleep Cycle?

It might seem like we adults simply fall asleep and then wake up in the morning. But, in reality, we go through different stages of sleep. In one “sleep cycle,” we go through four stages:

  • Stage 1 is Non-REM sleep and some call it “twilight sleep.” If someone disturbs you during this stage, you might not even feel like you fell asleep and it’s quite easy to wake up. We typically only spend a few minutes in this stage.
  • Stage 2 is also Non-REM and where we spend about half of our sleep. It is when our body temperature drops, our muscles begin to relax, and our eye movement stops.
  • Stage 3 is also Non-REM and deep sleep. Consequently, it is difficult to wake someone up during this stage. We typically spend the most time in deep sleep in the first half of the night.
  • Stage 4 is REM (Rapid Eye Movement) sleep and when most vivid dreams occur. REM sleep is considered “active” sleep when you might see limbs twitching whereas Non-REM sleep is considered “quiet sleep” when we look more peaceful. Even though we are dreaming, our muscles are paralyzed so we don’t act out those dreams. As the night progresses, we spend less time in Stage 3 and more time in Stage 4.

Although all people go through all of these stages of sleep, each night is different for each person. No two nights are the same nor do two people sleep the same. The amount of time you spend in each stage will vary throughout the night and change from night-to-night.

Babies also go through these stages but sleep cycles are different depending on age and are shorter.

How Are Sleep Cycles Different in Babies?

As you know, newborns typically sleep a lot, up to 16-18 hours a day. Newborns go immediately into REM sleep once they fall asleep and spend approximately 50% of their time in REM sleep. Therefore, it is why many newborns can sleep through noise. Since they spend 50% in REM and 50% in Non-REM deep sleep, it is often difficult to wake them. Because newborns are not going through the same four sleep cycles above, they typically sleep better and we get the old adage “sleeping like a baby.”

In reality, it should have been “sleeping like a newborn” because as your newborn grows, they start to sleep more like an adult. Babies begin to go into Non-REM sleep first and they go through the same four stages of sleep. This development begins around 3-4 months old and often leads to the 4 month sleep regression. It is between sleep cycles that a baby will have trouble staying asleep.

Because we are in deep sleep much of the time in the first half of the night, this often leads to babies sleeping through the night for 5-hour stretches fairly early. However, for the remainder of the night, they are cycling through the different stages and that’s where we start to see babies waking frequently at night.

How Long are Sleep Cycles in Babies?

While adult sleep cycles are usually around 90 minutes, babies have shorter sleep cycles. Baby sleep cycles are usually 40-50 minutes and vary by time of day and each night. This is often why babies take short naps. Catnapping is one of the most common complaints among new parents who visit this site.

Since children spend 1-2 hours in deep sleep, if your baby is waking at night, you might find they wake every 1-2 hours all night. This was the case for my son who inspired this website.

Also, we frequently hear from parents that their baby wakes even more frequently as we approach early morning. This is, again, because we spend a lot of time in deep sleep in the first part of the night. Therefore, 4:00 to 6:00 a.m. is often the most challenging for many families. A baby waking too early is one of the most common and difficult sleep problems to solve! Children who wake up after Stage 3 in the early morning are likely waking up crying whereas babies who enter Stage 4 before waking for the day wake up happy and refreshed.

Baby Sleep Cycles By Age Chart

Age Total Sleep Per Day Sleep Cycle Length Additional Resource
0-4 Weeks 15-18 hours N/A (see above) Essential Keys to Your Newborn’s Sleep
5-8 Weeks 15-18 hours N/A (see above) Newborn Schedules By Week
9-12 Weeks 14-17 hours 40 minutes 2-3 Month Old Baby Sleep Guide
3-4 Months 14-15 hours 40-50 minutes 4-Month Sleep Regression
5-6 Months 14-15 hours 40-50 minutess Mastering Naps & Schedules
7 Months 13-14 hours 40-50 minutes How to Handle Your Baby’s Separation Anxiety
8-10 Months 13-14 hours 40-50 minutes 8/9/10 Month Sleep Regression
11-13 Months 12-14 hours 45-60 minutes 12 Month Sleep Regression and Why Not All 12 Month Olds Transition to One Nap
15-18 Months 12-14 hours 45-60 minutes 18 Month Sleep Regression
18 Months to 2 Years 12-14 hours 60-75 minutes 2 Year Sleep Regressions
3-5 Years 11-13 hours 60-90 minutes 3 Signs Your Toddler Is Ready To Stop Napping

Please Note: This chart has been developed based on research, anecdotal experience as a sleep consultant, and extrapolating that a child’s sleep cycle is around 40 minutes at 3 months old and extends to approximately 90 minutes by 5 years old.

When Do Baby Sleep Cycles Lengthen?

Your child’s sleep cycles will gradually lengthen from 40-50 minutes to 90 minutes by the time they are around 5 years old.

How Many Sleep Cycles Should a Baby Have?

Most babies need 10-12 hours of sleep so that would equal approximately 12-14 sleep cycles each night. At nap time, they typically have 1-3 sleep cycles depending on age and the time of day.

When Do Babies Connect Sleep Cycles for Naps?

At nap time, there are a variety of reasons that babies don’t connect sleep cycles. Between 2-3 months old, most babies take short naps to spread out their daytime sleep over more periods during the day since they can’t stay awake long. As your baby approaches 4 months, 5 months, and 6 months old, they will start to connect sleep cycles for naps and take at least two 1+ hour long naps.

When Baby Wakes After Their First Sleep Cycle

If your baby is waking up after their first sleep cycle, this likely means they have a scheduling problem. Review their sleep schedule for their age to make sure you aren’t keeping them awake too long before their nap or bedtime.

If your baby is waking up happy after a 40-minute nap, this might mean they feel refreshed and they need to be awake longer before their nap.

How to Connect Sleep Cycles

To help your baby connect sleep cycles, you will want to teach your baby to fall asleep on their own first and foremost. Be sure to review all of the most common napping mistakes to help your baby take longer naps.

If your baby is waking at night, be sure to learn ways to help your baby sleep through the night.

Solve Your Child’s Sleep Problems by Richard Ferber

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