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What does research say about sleep training vs co-sleeping?

As both a mom of three and healthcare professional, I know how overwhelming and emotional sleep decisions can feel. Social media is filled with strong opinions, often leaving parents worried that one sleep choice could determine their child’s attachment, emotional health, or future development.

The good news is that the research is reassuring.

Our littles thrive when they are loved, cared for, and responded to consistently, regardless of how they sleep. The studies below explore what we currently know about infant sleep, attachment, co-sleeping, independent sleep, parental well-being, and healthy child development. I’ve summarized them in a simple sentence with the link attached so you can make informed decisions with confidence when it comes to sleep training vs co-sleeping.

Sleep and learning

Napping is essential for learning and memory.

Sleep caused better retention of statistical language learning in 6.5 month old infants

Sleep deprivation can demonstrate an intoxicated brain.

Infant sleep is vital for learning and growth.

Sleep isn’t simply “rest.” During sleep, babies’ brains are actively processing, organizing, and storing what they learned while awake.

Sleep is one of the most important things babies do for learning and development. During sleep, the brain actively processes information, strengthens memories, and supports growth.

Sleep and behavior

Babies who sleep well at night are more approachable, flexible, and have an easier temperament.

Later bedtimes and interrupted sleep can cause or increase social and emotional problems in children.

This research found that sleep training provided significant sleep benefits while causing no negative stress responses (measured by cortisol), long-term effects on attachment, or impacts on the child’s behavior.

Podcast episode that looks at sleep training and cortisol.

Sleep and Maternal Health

Postpartum sleep disturbance can affect maternal responsiveness.

Better infant sleep can improve maternal stress, anxiety, and depression.

Bond and Secure attachment

Sleep training does not negatively impact attachment as long as physical needs are met.https://pmc.ncbi.nlm.nih.gov/articles/PMC2724160/

Sleep and health

Good sleep improves immune response.

Sleep and family balance

This research demonstrates that (in 52 studies) sleep training resulted in better sleep for babies and also improved both the baby and family’s well-being.

Co-sleeping and attachment

While co-sleeping may offer benefits for some families, current research has not demonstrated that bed-sharing alone creates stronger attachment.

Research findings are mixed, and it remains unclear whether bed-sharing itself influences attachment or whether other parenting factors are responsible.

Co-sleeping was more common among children with anxiety, but the relationship between co-sleeping and emotional well-being is complex and does not support simple conclusions about co-sleeping improving emotional security.

The bottom line

Our babies and toddlers can develop secure attachment while co-sleeping, room-sharing, or sleeping independently. The strongest predictor of attachment is the quality of the caregiver-child relationship, not where a child sleeps.

If you have a little one on the way, grab a copy of my FREE Newborn Sleep Guide below. This will set you up with a solid sleep foundation to give your family the gift of rest.