"Cry It Out" Myths Debunked: What Research Really Says About Sleep Training

The Cry It Out (CIO) method, often associated with Dr. Richard Ferber, has been a popular sleep training approach for decades. This method suggests that allowing babies to cry themselves to sleep helps them learn to self-soothe. However, recent scientific research indicates that this practice can be detrimental to a child's development and overall well-being. This article explores the scientific evidence against the CIO method, incorporating insights from leading experts such as Professor James McKenna and Dr. Margot Sunderland.

Infant Brain Development and Self-Soothing

To understand why the CIO method can be harmful, it is essential to examine infant brain development. The prefrontal cortex, which is responsible for self-regulation and soothing, is not fully developed in infants. According to a study published in the journal Pediatrics, this part of the brain does not mature until later in childhood, indicating that babies are not neurologically equipped to self-soothe on their own. This underdevelopment is why infants naturally seek external comfort from their caregivers.

The Importance of Responsive Parenting

Infants learn to regulate their emotions and stress responses through interactions with responsive caregivers. Dr. Margot Sunderland, author of The Science of Parenting, emphasizes that parental responsiveness is crucial for healthy brain development. When parents respond to their baby's cries, they help build neural pathways that support emotional regulation, laying the foundation for a healthy stress response system.

Responsive parenting involves recognizing and meeting the needs of the infant promptly and consistently. This interaction is not just about stopping the crying but about providing the necessary comfort that helps in forming secure attachments. These secure attachments, in turn, foster trust and emotional stability, which are critical for long-term mental health.

Insights from Professor James McKenna

Professor James McKenna, a prominent expert in infant sleep, has extensively studied the effects of the CIO method. In his book Sleeping with Your Baby: A Parent's Guide to Co-Sleeping, McKenna argues that infants are biologically programmed to wake up during the night and seek comfort from their parents. He suggests that allowing babies to cry it out can lead to a state of shutdown, where they cease crying not because they have learned to self-soothe, but because their stress response system has been overwhelmed.

McKenna's research highlights that this shutdown is a defense mechanism rather than a sign of successful sleep training. When babies stop crying, it may appear that they have learned to sleep independently. However, this quietness can be a sign that the infant is experiencing high levels of stress, which could have long-term negative effects on their emotional and psychological well-being.

The Illusion of Sleep Training Success

A study published in Developmental Psychobiology found that sleep-trained infants wake up as often as non-sleep-trained infants during the night. The difference is that sleep-trained babies have learned not to signal their parents when they wake up, leading parents to believe their children are sleeping through the night. This misconception can result in unmet needs and prolonged stress for the infant.

The study's findings suggest that the perceived success of the CIO method is more about parental perception than actual improvement in the child's sleep quality. Parents may believe that their child is sleeping better because they are not being woken up by cries, but the infant is still experiencing disruptions. These disruptions can have cumulative effects on the child's development, potentially leading to issues with sleep patterns and emotional regulation later in life.

Long-Term Effects of Elevated Stress

When babies are left to cry without comfort, their bodies produce high levels of cortisol, a stress hormone. Chronic elevation of cortisol can have long-term effects on brain development and emotional health. Dr. Sunderland's research indicates that prolonged periods of crying without parental intervention can lead to an overactive stress response system, increasing the risk of anxiety and emotional disorders later in life.

Elevated cortisol levels can also affect the physical development of the brain, particularly in areas related to memory, learning, and emotional regulation. Over time, this can lead to difficulties in managing stress, forming relationships, and achieving academic success. Therefore, the CIO method, by promoting prolonged stress in infants, can inadvertently set the stage for a range of developmental challenges.

Cultural Perspectives and Historical Context

It's also worth considering the cultural and historical context of infant care practices. In many traditional societies, infants are rarely left to cry alone. Instead, they are kept close to caregivers through practices such as co-sleeping and babywearing, which provide constant comfort and reassurance. These practices align with the biological needs of infants for continuous parental presence and responsiveness.

Historical evidence suggests that the modern Western approach to sleep training, including the CIO method, is relatively recent and not aligned with the practices that have been successful in ensuring infant survival and development for millennia. Understanding this context can help parents make more informed decisions that are in harmony with the natural needs of their children.

The scientific evidence against the Cry It Out method is compelling. Infants are not neurologically equipped to self-soothe and require responsive caregiving to develop healthy emotional regulation. Experts like Professor James McKenna and Dr. Margot Sunderland highlight the potential harms of CIO, including increased stress and long-term emotional consequences. Responsive parenting not only fosters secure attachments but also promotes healthier sleep patterns for both infants and parents.

Choosing a sleep method that aligns with your family's values and your child's developmental needs is crucial. By prioritizing responsiveness and understanding the importance of brain development, we can support our children's growth and foster a more connected and emotionally healthy future.


  1. Pediatrics, Journal Article on Infant Brain Development
  2. Sunderland, M. (2006). The Science of Parenting. DK Publishing.
  3. McKenna, J. (2007). Sleeping with Your Baby: A Parent's Guide to Co-Sleeping. Platypus Media.
  4. Developmental Psychobiology, Study on Sleep-Trained Infants
  5. Journal of Child Psychology and Psychiatry, Study on Cortisol Levels in Infants