When your baby struggles to settle, wakes frequently at night, or cries for long periods, it’s easy to feel like you’re doing something wrong. But new research from a large twin study published in The Journal of Child Psychology and Psychiatry (Viktorsson et al., 2025) reveals that many early sleep and crying behaviors are shaped not just by parenting or environment, but by your baby’s genetics too.

Understanding this balance between nature and nurture can help parents feel more confident, knowing that some challenges are simply part of their baby’s unique make-up—and that the right environment and routines can still make a huge difference.

What the Study Found

Researchers studied nearly 1,000 twins at 2 and 5 months of age to untangle the genetic and environmental influences on:

• Sleep quality and number of night wake-ups
• Ability to settle
• Crying duration

The findings were fascinating:

• Crying duration is strongly influenced by genetics. Some babies are simply wired to cry more, regardless of parenting style.
• Settling ability shifts with age. At 2 months, settling was mostly influenced by the environment (bedtime routines, soothing techniques, sleep space). By 5 months, genetics played a larger role.
• Night wake-ups are largely environmental. Factors like feeding habits, sleep associations, and sleep environment account for most of the variation in how often babies wake at night.

What This Means for Parents

The first few months of life are a highly “plastic” period, meaning your baby’s brain and body are changing rapidly. While some babies are naturally better at self-regulating and sleeping for longer stretches, the environment you create—your routines, responses, and sleep setup—can significantly impact how well your baby sleeps.

For example, twins who shared the same home environment tended to have similar numbers of night wake-ups, suggesting that parental practices (like where and how babies are put to sleep) are crucial for night sleep.

This means parents can’t change their baby’s temperament or genetic wiring, but they can shape the environment to improve sleep outcomes.

Practical Takeaways for Better Sleep

Based on the study, here are some steps parents can take to work with their baby’s natural tendencies:

1. Focus on the Environment

At 2–3 months, environmental factors (like bedtime routine and sleep space) have the biggest influence. Creating consistent bedtime cues—such as a warm bath, a darkened room, and a white noise machine—can make settling easier.

2. Don’t Compare Babies

Some babies cry more or take longer to learn to self-soothe because of genetic differences. Comparing your baby to others can lead to frustration. Instead, focus on progress and patterns unique to your child. Especially during sleep training. Just because your friends baby only took 2 days and your baby is gradually progressing over a week doesn’t mean one is broken.

3. Support Self-Settling Skills

By 4–5 months, babies begin developing more independent settling abilities, but genetics play a bigger role here. Gentle sleep coaching techniques can help nudge these skills along while respecting your baby’s natural temperament. Take our temperament quiz to ensure you are working with your babies temperament.

4. Manage Night Waking's with Routine

Since night wake-ups are more environmental, this is where routine and sleep associations are key. If your baby wakes frequently, look at how they’re falling asleep—rocking or feeding to sleep can lead to more wake-ups compared to falling asleep in their cot. Consistency at night, how you choose to respond will create consistent nights. Focusing on consistent patterns that encourage longer nights will be be worth its weight in gold in the coming months.

Take my sleeping through the night masterclass to start this process. 

Crying and Colic: It’s Not Your Fault

The study also found that prolonged crying—especially in the evening—is partly genetic. For some babies, this can be linked to conditions like colic. This doesn’t mean that nothing can help, but it does mean that excessive crying isn’t a reflection of poor parenting.

As a sleep consultant, I see so many families who feel guilty or exhausted by their baby’s crying patterns. Research like this reminds us that while we can’t control everything, we can still create the best conditions for calmer, more settled sleep.

My deep dive into colic research is one of our most popular reads, check it out.

When to Seek Support

If your baby is consistently crying for long periods, waking frequently, or struggling to settle, professional support can make a huge difference. Early intervention not only improves sleep but can also reduce stress for the whole family.

This new research shows that while some sleep challenges are genetic, many aspects—especially night waking—are highly influenced by what happens at home. By understanding your baby’s unique temperament and creating the right environment, better sleep is possible.

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