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By Ciprian H. · checked against CDC, AAP and NHS guidance · how we fact-check

Published 3 min read

Baby separation anxiety by age: when it starts, peaks, and eases

Last verified: September 30, 2026

The short answer

Separation anxiety usually starts around 6 to 9 months, often peaks between 9 and 18 months, and settles through toddlerhood. It is a milestone, not a setback: your baby has figured out that you are their person and that you still exist when you leave. The NHS calls it a normal part of development and usually a sign of how well you have bonded.

Illustration of a large hand and a small hand reaching toward a heart

Why it happens, and why it is good news

For the first few months, most babies are happy to be held by almost anyone. Then, often somewhere around 6 to 9 months, that flips. Your baby protests when you leave the room, eyes strangers with suspicion, and wants only you. It can feel like a step backward. It is the opposite.

“Is shy, clingy, or fearful around strangers” and “reacts when you leave” are on the CDC’s official list of what most babies do by 9 months (CDC milestone checklists, scientific basis in Zubler et al., Pediatrics 2022). Two big things have clicked into place: you are their person, and people still exist even when they cannot be seen. The crying at the door is that new understanding, out loud.

The NHS puts it plainly: separation anxiety is common from around 6 months to 3 years, it is a normal part of development, and it is usually a sign of how well you have bonded (NHS: Separation anxiety).

Roughly how it changes with age

Every baby is different, and these are broad patterns, not a schedule:

  • Before about 6 months: usually little separation anxiety yet. Object permanence, the sense that things still exist when out of sight, is still forming.
  • Around 6 to 9 months: the classic onset. Clinginess and stranger wariness appear, right as the CDC 9-month milestones describe them.
  • Around 9 to 18 months: often the peak. Drop-offs and bedtimes can get harder, sometimes in waves that come and go with new skills, teething, or changes in routine.
  • Through the toddler years: it gradually eases as your child builds a reliable sense that you leave and you come back.

Because it overlaps with the busiest stretch of physical development, it can arrive alongside crawling, standing, and first words. Our window 4 guide covers that whole bundle of change together.

When it shows up at bedtime

Separation anxiety does not only happen at the front door. It is one of the common reasons bedtime and night waking get harder for a while in the second half of the first year: being left in the cot is a separation too. This is often what is behind a so-called sleep regression at this age. If that is where you are, our guides on sleep regressions by age and when babies sleep through the night cover it, and the same calm routine that helps daytime separations helps at night.

What helps

The NHS suggests a handful of things that genuinely make separations easier (NHS):

  • Practise short separations first. A few minutes with someone your baby knows well, then build up gradually.
  • Leave a comfort object. Something that smells or feels like you, or a favourite toy.
  • Say goodbye with a smile and confidence, even if your heart is breaking a little. Babies read your tension, so a calm, brief goodbye reassures more than a long anxious one.
  • Make reunions warm and happy, so the pattern “leaves, then comes back, and it is good” sinks in.
  • Keep routines predictable. The more your baby can predict the day, the safer separations feel.

One thing that does not help: sneaking out. Slipping away without a goodbye can make a baby more clingy, because they learn you might vanish at any moment. A short, cheerful goodbye teaches the more reassuring lesson.

On paper

Want to know which windows tend to bring the big feelings, so clinginess never blindsides you? The First-Year Map lays out the five development windows and the research landmarks on 11 calm pages, with every source cited. $8.50 USD, 50% off until November 30 (regular price $17 USD)$17 USD. Instant download on Gumroad.

When to talk to a professional

Talk with your doctor

The NHS suggests talking to your health professional if your child is very distressed, stays upset for a long time after you leave, or the difficulty goes on for more than a few weeks ([NHS](https://www.nhs.uk/baby/babys-development/behaviour/separation-anxiety/)). That is a conversation, not an alarm.

And as always: your own concern is reason enough to ask.

Keep reading

Sources

Peanutbean provides general information for educational purposes only. It is not medical advice. Every baby develops at their own pace. Always talk to your pediatrician about your child’s health.

Common questions

At what age does separation anxiety start in babies?

It commonly begins around 6 to 9 months, often peaks somewhere between 9 and 18 months, and eases through the toddler years. The NHS describes it as common from around 6 months to 3 years and a normal part of development.

Is separation anxiety a bad sign?

No. Being clingy and wary of strangers is on the CDC's 9-month milestone list and is usually a sign of healthy bonding. It means your baby has worked out that you are their person and that you still exist when you leave the room.

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Peanutbean provides general information for educational purposes only. It is not medical advice. Every baby develops at their own pace. Always talk to your pediatrician about your child's health.