At what ages do sleep regressions happen, and are there really that many?

Online you'll find lists with six, eight or ten sleep regressions: at four months, six, eight, ten, twelve, eighteen, two years. It reads as if your child spends the first year almost permanently in a regression.

That isn't right, and the difference is useful.

There is one that changes sleep itself

The four-month sleep regression is the only one that deserves its name. That's when sleep structure changes permanently: the sleep cycle starts to resemble an adult's, with a light moment at the end of every cycle. That doesn't go away. It isn't a phase but a new foundation.

It's worked out separately in the four-month sleep regression.

The rest are leaps and milestones

All the other periods called a "regression" are something else: a mental leap, a motor milestone, or both at once. Kyra says it this way in the lesson on six to eight months too: sleep regressions are temporary and belong to this phase.

What's really going on, period by period:

• Around 6 to 8 months. Rolling, sitting and crawling get going, and separation anxiety gets stronger. That's leap 6.
• Around 9 to 12 months. Crawling and pulling up, then standing and the first steps. Kyra: the brain keeps practicing crawling and standing even at night. That's leap 7.
• Around 12 to 18 months. Planning, walking, talking, and the switch from two naps to one. See leap 8 and toddler wake windows.
• Around two years. Testing limits, imagination and fears. See afraid of the dark and the toddler who won't sleep.

Why that distinction matters

With the four-month regression, something lasting changes, and then your approach has to change along with it: a new skill is needed, namely falling back asleep on their own.

With the rest, there's nothing new to learn. There the task is precisely to change nothing: hold on to the routine, give extra comfort, and wait for it to settle. If you try something different in every phase, you build a habit in two weeks that then has to be undone again.

The rule that's almost always right

Don't look at the age but at what your child is learning. If a new movement is on its way, rolling, sitting, crawling, standing, that's your explanation.

Kyra adds a detail many parents recognize: it's often worst just before the skill is really there. As soon as crawling or sitting works, the restlessness settles again.

So practicing during the day is the shortest way out. See milestones and poor sleep.

When it isn't a phase after all

If it lasts longer than a few weeks, or doesn't match any milestone, look at the daily rhythm first. Overtiredness looks like every regression: wake windows by age.

And go through the list of the three signs, because then you'll know whether a leap is going on: Wonder Weeks and sleep.