When Do Sleep Regressions Happen?

When my oldest boy experienced his first major sleep regression, it made me wonder – is this a one-time thing or will it happen again? Is there a way to predict if this will happen again? When do sleep regressions even happen?

Sleep regressions most commonly occur in tandem with major developmental milestones. The most common sleep regressions happen at about 4 months old, 8-10 months old, and 18 months old. Some children may experience more sleep regressions than that, while others may not experience as many noticeable sleep disruptions.

So let’s talk more about when the common, major, and less-common sleep regressions happen.

An image of a bored young kid lying on a couch next to his young worried parents. — Young tired woman sitting on the bed near the children’s cot.

When Are the Major Sleep Regressions?

The major (or most common) sleep regressions typically happen at 3 ages:

At about 4 months old
Between 8-10 months old
At about 18 months old

These line up with 3 major developmental milestones:

Normal (and permanent) sleep pattern changes related to brain development
Learning to stand and/or walk (with or without assistance)
18-month-old separation anxiety and exertion of control

The reason why these ages sleep regressions happen at an age range (rather than at a specific month or even week of development) is that all children develop at different speeds.

Thus, having an age range (and knowing the triggering event) tends to be more helpful to a wider range of parents.

Each of these stages in development is totally normal – as is having a short period of associated sleep disturbance. (If you’d like to read the scientific literature and evidence on sleep regressions, you can read my article on that right here.)

Otherwise, let’s address the next question: does each child go through each sleep regression?

Do All Babies Go Through the 4-Month Sleep Regression?

Almost all babies will experience some sort of sleep disturbance or sleep regression at 4 months of age. This is because the 4-month-old sleep regression happens as your child’s brain naturally matures – and becomes capable of sleeping more like an adult than a baby.

So while most babies will experience this particular sleep regression, there’s a very wide range of ways in which your baby could react to it. This spectrum is usually divided into three groups.

Here are the three ways in which most babies will react to the 4-month-old sleep regression:

Naturally easy sleepers may simply slide from their baby sleep patterns into a more developed one – with little-to-no disturbances at all.
Average sleepers may experience a small disturbance in their sleeping pattern before adjusting to the more adult-like sleep patterns.
Naturally difficult sleepers may experience a harder time shifting into more adult-like sleep patterns.

According to sleep disturbance studies, the first two groups make up about 70-80% of all children, depending on which study you reference.

The last group of babies is the 20-30% of babies that have more pronounced sleep issues. This group is one that has not had anything close to a reliable sleeping pattern. These are the babies that will experience a big, noticeable, and life-changing sleep regression at four months. It may take several weeks (up to a month) for things to calm down again.

Thankfully, though, this is the age when appropriate and safe sleep training methods may begin to be used with successful outcomes.

Do All Babies Go Through the 8-10 Month Sleep Regression?

Most babies will probably experience some level of sleep disturbance or sleep regression between 8 and 10 months of age. This is because there are several developmental milestones that occur at this age, almost all of which involve increased mobility – and this increased mobility is especially disrupting at night.

Even so, there’s still a very wide range of ways in which this increased mobility affects each baby’s sleep disturbances.

Naturally easy sleepers may self-adjust to these increases in mobility with little-to-no nighttime sleep disturbances at all.
Average sleepers may experience a small-to-medium-sized disturbance in their sleeping patterns before adjusting with only some parental involvement.
Naturally difficult sleepers may experience a harder time self-soothing back to sleep and may require more involved parental help via sleep training.

According to sleep disturbance studies, the first two groups make up about 70-80% of all children, depending on which study you reference.

Do All Babies Go Through the 18-Month Sleep Regression?

At 18 months of age, most toddlers will experience another major sleep regression. This one correlates to the natural development of:

A toddler’s new ability to express opinions
Normal development of separation anxiety
Teething pain, due to erupting molars

At this age, a baby’s natural sleep level has much less effect on the length and power of the sleep regression than do your toddler’s temperament, ability to self-soothe, and other family dynamics (like parenting styles).

In other words, your toddler now has a more pronounced opinion about naps and bedtime – and they aren’t afraid to yell it, even if it’s just: “NO!”

Depending on your toddler’s ability to self-soothe, their temperament, and your parenting style, this sleep regression may last merely a few days or it may last much longer. In some cases, it may even take months to get sleep schedules back onto a healthy pattern.

At What Other Ages Can a Baby Experience a Sleep Regression?

Sleep regressions sleep disturbances or other sleep problems can happen at any time – not just during the 3 major sleep regressions we discussed above. They can happen almost any time – and can be triggered by various causes.

Let’s discuss each of those ages – followed by the causes.

Do Babies Experience a Sleep Regression Between 5-7 Months Old?

Not every child will experience a sleep regression between the ages of 5-7 months of age. However, some babies will experience another regression.

This is because, between 5-7 months of age, babies naturally hit several important milestones. Other issues that may trigger a regression at this age relate to how mobile a baby is becoming – both during the day and at night. Depending on the infant, these can include:

Rolling over
Sitting up
Crawling
Pulling up to stand
Removal of sleep aids like swaddling

For babies who have relied on sleep aids (like swaddling), their removal can be particularly difficult. Especially as that newfound nighttime mobility tends to cause more frequent nighttime wakings.

Anecdotal evidence shows that the likelihood of a sleep regression occurring between 5-7 months old depends on how well babies sleep at their baseline level. In other words, naturally easy sleepers are much less likely to have a long or noticeable sleep regression than are naturally difficult sleepers.

Depending on your baby’s natural sleep levels, each of these developmental milestones could cause a sleep disturbance or sleep regression. These sleep regressions could last anywhere from a few days to a few weeks.

The 10-11-Month-Old Sleep Regression

Many babies will experience a sleep regression at about 10-11 months of age.

Sleep regression caused at this age may continue to be linked to developmental milestones, although it can also be caused by several other factors, including time changes, travel, and illness. We’ll discuss these factors further along in the article.

According to anecdotal research and my own surveys of more than 700 parents, naturally easy sleepers are more likely to have fewer sleep regressions, sleep disturbances, and problems at night. Average sleepers may experience a few rough nights with a sleep regression, but it generally self-resolves. More-difficult sleepers may experience more difficult, noticeable, or prolonged sleep regressions that require parental involvement (via sleep training).

In my opinion, this is one of the worst sleep regressions and it ought to be considered one of the major sleep regressions due to its severity for those that do experience it. However, because it’s only so pronounced for the more naturally difficult sleepers, it’s not being included among the major sleep regressions.

Get more ideas to deal with this difficult sleep regression – read my article here about 30 things to know about the 11-month-old sleep regression.

Do Babies Experience a Sleep Regression Between 12-17 Months Old?

Some babies will experience a sleep regression – or multiple sleep regressions – between 12 and 17 months of age. During this time, sleep regressions seem still to be somewhat correlated with how well a baby sleeps naturally, although the correlation is lessening dramatically.

This correlation is quickly being supplanted or replaced by your child’s temperament, ability to self-soothe, and family dynamics like parenting styles.

The 2-Year-Old Sleep Regression

Some 2-year-olds experience another sleep regression that is highly reminiscent of the 18-month sleep regression, but with a better vocabulary and a faster-running child.

Again, this sleep regression is more related to your child’s temperament, ability to self-soothe, and family dynamics (like parenting styles) than their natural sleep ability. This sleep regression may also be related to room-sharing, new siblings, or other life changes.

This sleep regression may last anywhere from a few days to much longer, depending on the above factors.

Toddler Sleep Regressions

Toddlers, or children from about 1 to 3 years old, may experience sleep regressions from time to time. These sleep regressions are usually related to anxiety, sickness, travel, and time changes.

Sleep regressions for a toddler may last from a few days to a few weeks, depending on their ability to self-soothe, temperament, and family dynamics.

Preschool and School-aged Sleep Regressions

Preschool and school-aged children may experience occasional sleep regressions. By this age, sleep regressions are almost always caused by anxiety, fears, fear of missing out, travel, time changes, or sickness.

Preschool and school-aged sleep regressions may last anywhere from a couple of nights up to a couple of weeks. Mitigating factors continue to be the ability to self-soothe, the child’s temperament, and family dynamics.

When Do Other Sleep Regressions Take Place?

Looking beyond age-related sleep regressions, there are a handful of main situations when a sleep regression is likely to occur. These times are:

Time changes
Travel or vacation
Illness, sickness, or teething
Anxiety or Fear

Let’s talk about each of these.

Time Changes May Trigger a Sleep Regression

Changing time may trigger a sleep regression for any and everyone involved – adults and children alike. This is because the physical change in time does not always line up with our natural circadian rhythm, or our sleep-wake cycle.

Adjusting to the new time, whether via something like daylight savings or simply moving into a different time zone, takes time to adjust. This may take a few nights or several weeks, depending on the individual person and how long it takes for their circadian rhythm to adjust to the clock.

Travel and Vacation May Trigger a Sleep Regression

Travel and vacation may also cause sleep regression for two main reasons:

Travel involves a significant change from usual behaviors and schedules
Travel often involves a time change

For children, a deviation from the usual schedule or routine often causes worry and anxiety, no matter how fun the vacation is. This can cause difficulties in sleeping and therefore sleep regression.

If travel involves a time change, this can also trigger a sleep regression. If the amount of travel is significant, there can also be jet lag involved, which will further worsen the sleep regression.

In this case, the sleep regression will begin with the travel and may take several days or weeks after the event to resolve.

An image of a Baby girl with a teething toy.

Illness, Sickness, and Teething May Trigger a Sleep Regression

Sickness, illness, and teething may also trigger a sleep regression due to their impact on sleep’s length, depth, and impact on being well-rested. For example:

Teething can be quite painful – at least until the tooth erupts. Once that has been resolved, the child will be able to begin sleeping better.
Colds result in a significant amount of stuffiness that can affect a child’s ability to breathe (and sleep) well at night.

Once the illness or teething has been resolved, the sleep regression should self-resolve within a few days. Or in more severe conditions, parental involvement via sleep training may be necessary to help it resolve within a matter of weeks.

Anxiety and Fear Trigger Sleep Regressions From Age 3-4+

Once children are able to start pretending, fears can become real to them. This can be via nightmares (or night terrors), anxiety, or a fear of missing out on something fun.

These fears and anxieties can trigger sleep regressions that will be both lasting and very disruptive – at least until the underlying fear or anxiety can be addressed and calmed.