Is sleep training, Cry it Out or Ferber method, harmful? The science behind it.

I want to give an unbiased opinion about sleep training, especially the Cry It Out or Ferber methods, so you can make your own decision. It seems that everywhere on the internet, people are either against it or for it. But as I promise to you, here, what you will get is only unbiased information based on studies and research that were made and not opinions of people.

If you are not familiar with the sleep training methods here is my article Understanding sleep training: Ferber, Cry It Out, and Gentle approaches. See below an overview of main sleep training methods that involve crying.

From the body of research existing today:

TLDR; If sleep training (mainly the Cry it Out and Ferber methods) does not yield results within a week, it is crucial to stop, as leaving your baby to cry for extended periods increases prolonged stress, which is proven to cause long-term harm! Responsive caregiving should be your long term approach.

Unbiased key takeaways

1. Immediate stress response: Studies have shown that infants subjected to crying sleep training methods experience elevated cortisol levels, indicating significant stress during the initial training days
2. Proven effectiveness: Research consistently supports the effectiveness of the Cry It Out (CIO) and the Ferber methods in dramatically reducing night wakings and improving overall sleep quality
3. No short to medium-term harm: Comprehensive studies have found no evidence of cognitive, behavioral, or emotional short or medium-term impacts (up to 5 years) on babies who underwent sleep training
4. Uncertain long-term effects: There is a notable gap in the research concerning the long-term impacts of sleep training into adolescence and adulthood. More longitudinal studies are needed to fully understand these effects.
5. Chronic stress vs. short-term stress: Existing research highlights that chronic, continuous stress has detrimental effects on development. However, short-term stress, such as during brief sleep training, does not show the same harmful long-term consequences
6. Benefits of responsive parenting: Studies underline that the best outcomes for emotional and cognitive development are achieved through synchronous, responsive parenting—promptly addressing the baby’s needs
7. Consequences of night wakings: Persistent night wakings are linked to poor performance, anxiety, and other mental health issues in later life, emphasizing the importance of effective sleep training

Detailed Examination

1. Immediate stress response of Cry It Out

Studies, such as those by Middlemiss et al. (2012), have shown that infants subjected to crying sleep training methods experience elevated cortisol levels, indicating stress during the initial training days. The study found a significant increase in cortisol levels for both infants and their mothers during the extinction process, highlighting the stress experienced by both parties during Cry It Out (CIO) sleep training.

2. Proven effectiveness of Cry It Out

Research, including a meta-analysis by Mindell et al. (2006), supports the effectiveness of the Cry It Out (CIO) method in reducing night wakings and improving sleep quality. The analysis of 52 studies concluded that behavioral interventions, including CIO, significantly reduce bedtime resistance and night wakings within one week of implementation. Hiscock et al. (2008) also found that infants who underwent behavioral sleep training, including CIO, showed significant improvements in sleep patterns and reductions in night wakings, with sustained benefits observed up to 5 years later.

3. No short to medium-term harm of Cry It Out

There is no evidence of cognitive, behavioral, or emotional short or medium-term impact on babies that went through sleep training. Studies such as those by Price et al. (2012) and Hiscock et al. (2008) found no differences in emotional, behavioral, or cognitive measures between children who underwent sleep training and those who did not, up to five years after the intervention.

4. Uncertain long-term effects of Cry It Out

There are limited longitudinal studies specifically examining the long-term effects of Cry It Out (CIO) into adolescence and adulthood. The existing research, such as Hiscock et al. (2008), indicates no immediate adverse effects, but the long-term impacts remain speculative due to the lack of comprehensive longitudinal data.

5. Chronic stress vs. short-term stress of Cry It Out

Existing research suggests that early stress impacts later development, but it has to be chronic, continuous stress to cause significant harm. Chronic stress is associated with issues in emotional regulation, cognitive development, and increased risk of anxiety and depression. For instance, Gunnar and Quevedo (2007) emphasized that prolonged exposure to high cortisol levels due to chronic stress can adversely affect brain development, particularly the hippocampus and prefrontal cortex, which are crucial for memory and executive functions. However, short-term stress, such as that experienced during brief periods of sleep training, is generally not associated with long-term developmental issues. Studies suggest that short, acute stress episodes can be managed effectively by a supportive environment and do not lead to lasting harm (Lupien et al., 2009).

6. Benefits of responsive parenting

Research supports that the best outcome for emotional and cognitive development is achieved through synchronous, responsive parenting, meaning responding in a timely manner to the baby’s needs. Feldman (2007) found that infants who experienced consistent and responsive caregiving had better stress regulation, more secure attachment, and improved social and emotional outcomes compared to those who did not receive responsive caregiving.

7. Consequences of night wakings without any sleep training

Studies also suggest that frequent night wakings can lead to poor performance and anxiety in later life. Gregory et al. (2006) found that children with persistent sleep problems were more likely to experience anxiety and depression in adolescence. Touchette et al. (2007) linked frequent night wakings to cognitive and behavioral issues at school entry, indicating that disrupted sleep can have lasting impacts on academic and emotional development.

Conclusion

Based on my own judgment, and considering my certifications in safe sleep and infant brain development, implementing sleep training as a short-term strategy, such as for 3-4 days, is unlikely to cause any long-term adverse effects. Essentially, it is about balancing the stress the baby accumulates during 3-4 days (or up to a week) of training against the prolonged stress of frequent night wakings.

In this scenario, enduring the 3-4 days of stress appears more beneficial than prolonged stress from frequent night wakings. However, if sleep training does not yield results within a week, it is crucial to stop, as leaving your baby to cry for extended periods increases prolonged stress, which is proven to cause long-term harm.

The best approach for parenting in the long-term remains responsive caregiving, ensuring timely responses to the baby’s needs. While current evidence suggests that short-term sleep training can be beneficial without long-term harm, the long-term impact of sleep training methods still needs to be conclusively proven or disproven by further studies.

Studies referenced, so you can do your own research

1. Middlemiss, W., Granger, D. A., Goldberg, W. A., & Nathans, L. (2012). Asynchrony of mother–infant hypothalamic–pituitary–adrenal axis activity following extinction of infant crying responses. Early Human Development, 88(4), 227-232
2. Mindell, J. A., Kuhn, B., Lewin, D. S., Meltzer, L. J., & Sadeh, A. (2006). Behavioral treatment of bedtime problems and night wakings in infants and young children. Sleep, 29(10), 1263-1276.
3. Hiscock, H., & Wake, M. (2002). Randomised controlled trial of behavioural infant sleep intervention to improve infant sleep and maternal mood. BMJ, 324(7345), 1062-1065.
4. Price, A. M., Wake, M., Ukoumunne, O. C., & Hiscock, H. (2012). Five-year follow-up of harms and benefits of behavioral infant sleep intervention: randomized trial. Pediatrics, 130(4), 643-651.
5. Gunnar, M. R., & Quevedo, K. M. (2007). The neurobiology of stress and development. Annual Review of Psychology, 58, 145-173.
6. Feldman, R. (2007). Parent-infant synchrony and the construction of shared timing; physiological precursors, developmental outcomes, and risk conditions. Journal of Child Psychology and Psychiatry, 48(3-4), 329-354.
7. Gregory, A. M., & O’Connor, T. G. (2006). Sleep problems in childhood: a longitudinal study of developmental change and association with behavioral problems. Journal of the American Academy of Child & Adolescent Psychiatry,