Show Me The Science

Sleep training can be a hot button issue with lots of inflammatory statements, contradicting opinions, and mom-shame. Let’s cut right to the science and dive into what we can find from peer-reviewed research articles.


  1. Anisfeld, E., Casper, V., Nozyce, M., & Cunningham, N. (1990). Does Infant Carrying Promote Attachment? An Experimental Study of the Effects of Increased Physical Contact on the Development of Attachment. Child Development, 61(5), 1617–1627.
    1. This study looked at 49 mother-infant dyads from low SES and compared whether baby-wearing or leaving the baby in a seat promoted more secure attachment. They found that young babies who were carried more had more secure attachment at 13 months than those who were more often in a seat. This study shows that physical contact with your baby is important to attachment.
    2. Cassidy, J., & Shaver, P. R. (2016). Handbook of attachment: Theory, research, and clinical applications. New York, NY: The Guilford Press.
      1. This textbook provides a helpful baseline for understanding attachment theory. There are four main types of attachment:
          1. secure – confident in a parent’s availability, protection and comfort as a result of positive past experiences. This is the goal!
          2. insecure – extremely distressed in a parent’s physical or emotional absence and difficult to console when the parent is present, unsure whether their parent will provide protection and comfort
          3. avoidant – cool, somewhat tense and indifferent towards parents, indicating that their parents’ presence has no significant bearing on their emotional state
          4. disorganized – fearful, disoriented, and highly aggressive, often the result of parental neglect 
          5. Keep in mind: secure attachment is our goal, and it shows up over time. Just because your baby is distressed one day does not mean they have an insecure attachment style. They may just be having a rough day.

Baby Crying

  1. Barr, R. G., Konner, M., Bakeman, R., & Adamson, L. (1991). Crying in !kung San Infants: A Test of the Cultural Specificity Hypothesis. Developmental Medicine & Child Neurology, 33(7), 601–610.
    1. This study compared crying patterns from infants in a hunter-gatherer society to infants from an industrialized, Western society. They found that all babies cry more early in life, but differences in culture and caretaking impact how long they cry for at a time.
  2. Papoušek, M., & von Hofacker, N. (1998). Persistent crying in early infancy: Anon-trivial condition of risk for the developing mother-infant relationship. Child: Care, Health & Development, 24(5), 395–424.
    1. This study found that the following factors may predict infant crying: prenatal stress or anxiety, maternal psychopathology, partnership conflicts, low maternal self-efficacy, high maternal depression/anxiety/anger/ACEs/marital distress. While we cannot say these factors caused the child’s crying, they may have maintained it or can at least be tied to it in some way.
  3. Radesky, J. S., Zuckerman, B., Silverstein, M., Rivara, F. P., Barr, M., Taylor, J. A., Lengua, L. J., & Barr, R. G. (2013). Inconsolable Infant Crying and Maternal Postpartum Depressive Symptoms. PEDIATRICS, 131(6), e1857–e1864.
    1. This study looked at whether long bouts of crying had a different effect on maternal depression than colic (at least 3 hours of crying in a day). They found that it’s not as much about whether the baby cries, it’s about whether the mom can soothe the baby if she wants to (i.e. if she’s sleep training and allowing her baby to cry, she won’t feel as depressed as if she is incapable of getting her baby to calm down as happens with colic).
  4. St James-Roberts, I. (2006). Infant Crying and Sleeping in London, Copenhagen and When Parents Adopt a “Proximal” Form of Care. PEDIATRICS, 117(6), e1146–e1155.
    1. This study reinforces that baby crying is a normal part of development. Babies who have less physical contact with their parents cry most from 2-5 weeks old, meaning they need to be held more at that age. Babies who are held at an appropriate level will still go through a period of more crying, around 12 weeks. Parents who begin sleep training around 12 weeks old should expect more crying than usual simply due to their baby’s age.

Baby Sleep and Baby Outcomes 

  1. Henderson, J. M. T., France, K. G., Owens, J. L., & Blampied, N. M. (2010). Sleeping Through the Night: The Consolidation of Self-regulated Sleep Across the First Year of Life. Pediatrics, 126(5), e1081–e1087.
    1. This article looked at how baby sleep develops over the first year of life. They studied 75 infants and found that the biggest consolidation of sleep happens between 1-4 months old and that by 5 months old, about half of babies sleep at the same time as their parents.
  2. Hysing, M., Harvey, A. G., Torgersen, L., Ystrom, E., Reichborn-Kjennerud, T., & Sivertsen, B. (2014). Trajectories and Predictors of Nocturnal Awakenings and Sleep Duration in Infants. Journal of Developmental & Behavioral Pediatrics, 35(5), 309–316.
    1. This article says that 6-month-olds wake up more at night than 18-month-olds because of how they develop. However, babies who sleep in the same bed as their parent(s) are more likely to wake up at night, no matter the age.
  3. Ross, C.N. and K.H. Karraker. Effects of fatigue on infant emotional reactivity and regulation. Infant Mental Health Journal. 20(4): p. 410-428. 1999.
    1. This article says that tired babies are more emotionally reactive and less able to cope with emotions than well-rested babies. Because babies sleep so often and so much, it is important for parents to cope and help their babies cope with the emotional distress that can increase with fatigue.
  4. Spruyt, K., Aitken, R. J., So, K., Charlton, M., Adamson, T. M., & Horne, R. S. (2008). Relationship between sleep/wake patterns, temperament and overall development in term infants over the first year of life. Early human development, 84(5), 289-296.
    1. This study concludes that there is a relationship between infant temperament, sleep, and functioning, but it is unclear which variables predict the others. The study does not address sleep intervention, but it does say that improvements in sleep (in our case, through intervention) may be accompanied by improved functioning and/or more positive temperament.

Baby Sleep and Maternal Mental Health

  1. Bayer, J. K., Hiscock, H., Hampton, A., & Wake, M. (2007). Sleep problems in young infants and maternal mental and physical health. Journal of Paediatrics and Child Health, 43(1–2), 66–73.
    1. This study looked at 692 Australian mothers from various SES backgrounds and found no relationship between baby sleep problems and income level. They did find that moms’ physical and mental health was worse, the more sleep problems their baby had. Examples of sleep problems included baby waking every night in a week, nursing to sleep at bedtime, co-sleeping, and parental disagreement on how to manage their baby’s sleep. 
  2. Clifford, T. J., Campbell, M. K., Speechley, K. N., & Gorodzinsky, F. (2002). Sequelae of Infant Colic: Evidence of Transient Infant Distress and Absence of Lasting Effects on Maternal Mental Health. Archives of Pediatrics & Adolescent Medicine, 156(12), 1183–1188.
    1. Many babies with sleep problems are considered colicky, which adds to parental stress. This study found that about 85% of colic cases are resolved by 3 months of age, and colic does not seem to have a lasting effect on maternal mental health.
  3. Dennis, C.-L., & Ross, L. (2005). Relationships Among Infant Sleep Patterns, Maternal Fatigue, and Development of Depressive Symptomatology. Birth, 32(3), 187–193.
    1. This study looked at 505 mothers who did not show signs of clinical depression 1 week postpartum. At 4 and 8 weeks postpartum, moms who had begun showing signs of clinical depression also reported more sleep problems for their baby and themselves. This article shows a strong connection between baby sleep patterns, maternal sleep, and onset of postpartum depression in the first 8 weeks.
  4. Hiscock, H., Bayer, J., Gold, L., Hampton, A., Ukoumunne, O. C., & Wake, M. (2007). Improving infant sleep and maternal mental health: A cluster randomised trial. Archives of Disease in Childhood, 92(11), 952–958.
    1. This study pulled 328 Australian mothers from various SES levels with 7-month-old babies struggling with sleep. Mothers in the study who received home visits from a nurse to work through the sleep problems reported fewer problems and lower rates of depression when the baby was 12 months old. This study shows that behavioral sleep intervention can help improve baby sleep and maternal mental health.
  5. Hiscock, H., & Wake, M. (2001). Infant Sleep Problems and Postnatal Depression: A Community-Based Study. Pediatrics, 107(6), 1317–1322.
    1. This study of over 700 Australian mothers found a relationship between infant sleep problems and postpartum depression. Mothers who reported an infant sleep problem were over twice as likely to experience clinically significant symptoms of depression. Mothers who were getting good sleep despite baby sleep problems (having help at night, for example) were not more likely to experience depressive symptoms. 
  6. Eckerberg, B. Treatment of sleep problems in families with young children: effects of treatment on family well-being. Acta Paediatr. 93(1): p. 126-34. 2004.
    1. This study of 95 families in Sweden showed that babies can learn to fall asleep on their own at bedtime and then, once that’s familiar, when they wake up during the night. The study showed improved sleep, daytime behavior, and well-being for the entire family and is evidence of the benefits of sleep training!
  7. Wake, M., E. Morton-Allen, Z. Poulakis, H. Hiscock, S. Gallagher, and F. Oberklaid. Prevalence, stability, and outcomes of cryfuss and sleep problems in the first 2 years of life: prospective community-based study. Pediatrics. 117(3): p. 836-42. 2006.
    1. This study found that most baby sleep problems are short developmental stages, rather than lasting a long time. In this sample of middle-class, first-born infants, it was mainly the more lasting problems that predicted worse maternal mental health and stress levels.
  8. Hiscock, H., J.K. Bayer, A. Hampton, O.C. Ukoumunne, and M. Wake. Long-term mother and child mental health effects of a population-based infant sleep intervention: cluster randomized, controlled trial. Pediatrics. 122(3): p. e621-7. 2008
    1. This study showed one-fifth of the depression in mothers of babies who underwent a sleep intervention than those whose babies’ sleep problems were not addressed.

Maternal Mental Health and Relationship Quality

  1. Paulson, J. F., & Bazemore, S. D. (2010). Prenatal and Postpartum Depression in Fathers and Its Association With Maternal Depression: A Meta-analysis. JAMA, 303(19), 1961–1969.
    1. This article looked at studies of over 28,000 fathers who reported depression sometime between the first trimester and end of the first year of the baby’s life. They found that about 10% of men experience prenatal and/or postpartum depression. We need to remember that dads may struggle with depression too, and two parents with postpartum depression can lead to lower relationship quality.

Maternal Sleep and Maternal Mental Health

  1. Dørheim, S. K., Bondevik, G. T., Eberhard-Gran, M., & Bjorvatn, B. (2009). Sleep and Depression in Postpartum Women: A Population-Based Study. Sleep, 32(7), 847–855.
    1. This study looked at nearly 4,200 women at 7 weeks postpartum. They found that more sleep disturbances and worse overall sleep are likely to predict maternal depression.
  2. Swanson, L. M., Pickett, S. M., Flynn, H., & Armitage, R. (2011). Relationships Among Depression, Anxiety, and Insomnia Symptoms in Perinatal Women Seeking Mental Health Treatment. Journal of Women’s Health, 20(4), 553–558.
    1. This study used a sample of 257 women to determine that there is a strong relationship between sleep and mental health. Mothers with clinically significant insomnia were 7.7 times more likely to have symptoms of depression and 2.6 times more likely to have symptoms of anxiety than mothers with lower insomnia scores.

Relationship Quality and Child Outcomes

  1. Meijer, A. M., & van den Wittenboer, G. L. H. (2007). Contribution of infants’ sleep and crying to marital relationship of first-time parent couples in the 1st year after childbirth. Journal of Family Psychology, 21(1), 49–57.
    1. This study found that infant crying is a main predictor of relationship dissatisfaction and tension. Of course it is hard for couples to hear their baby cry! We would expect the long-term benefits of sleep training to outweigh the short-term costs to the relationship.
  2. James, S. L., Nelson, D. A., Jorgensen-Wells, M. A., & Calder, D. (2021). Marital quality over the life course and child well-being from childhood to early adolescence. Development and Psychopathology.
    1. This article says that consistently poor marriage quality has been linked to worse outcomes for children, such as worse self-regulation, academic performance, and health. Every relationship has its ups and downs, but if there are consistent problems, there may be implications for the children as well.

Sleep Training

  1. Hiscock, H., & Fisher, J. (2015). Sleeping like a baby? Infant sleep: Impact on caregivers and current controversies. Journal of Paediatrics and Child Health, 51(4), 361–364.
    1. This article says that sometimes we consider baby sleep to be a problem when really it’s just developmental. It is hard to measure harm that may come to babies from different sleep-training methods. More studies are needed that look at the same babies from these studies when they are older, to see any lasting effects.
  2. Hiscock, H., & Wake, M. (2002). Randomised controlled trial of behavioural infant sleep intervention to improve infant sleep and maternal mood. BMJ, 324(7345), 1062.
    1. This study surveyed 156 Australian mothers of infants aged 6-12 months who reported severe sleep problems. All mothers received some education on infant sleep, but half of the mothers also implemented controlled crying (responding to crying at gradually increasing intervals). Within 2 months, the controlled crying group had more resolved sleep problems and a larger drop in maternal depression scores. Within 4 months, the changes between groups were similar. This article shows that controlled crying can help mothers and babies over 6 months feel and sleep better.
  3. 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 induced during the transition to sleep. Early Human Development, 88(4), 227–232.
    1. This article looks at cortisol (stress hormone found in saliva) levels in moms and babies over three nights of extinction. The study found that for the first two nights, both moms and babies had high cortisol. For the third night, babies still had high cortisol but they stopped crying so much. Because the babies cried less, moms’ cortisol went down. This created a mismatch in cortisol levels where moms thought their babies were feeling better than they actually were. The article notes that cortisol levels would probably sync back up over time as the baby learned to self-settle (not just calm their behavior).
  4. 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.
    1. This article analyzed 52 studies, including over 2,500 participants. Almost all parents (94%) across studies said that behavioral interventions helped them improve bedtime problems and night wakings. Many of those parents (82%) said that interventions helped them for 3-6 months, which is plenty of time for the baby to grow into their next phase! The strategies most supported in the research were: graduated extinction (controlled crying), positive bedtime routines, scheduled awakenings, and parent education. The study also noted that sleep intervention helps improve parent sleep and mental health and parent-child relationships.
  5. Pantley, E. (2002). The No-Cry Sleep Solution. McGraw Hill.
    1. This book is popular for parents who want to help their babies learn to sleep without crying. The author gives several reasons that cry-it-out is bad for babies, including unmet emotional needs, it being a traumatic experience, and calling it “nighttime neglect.” The book cites one doctor and the author’s personal experience and research with 60 families, but it does not have much information on how she conducted the research or other literature that supports her claims. It primarily plays on parents’ emotions. We don’t teach leaving your baby to cry on its own for hours, but a much more mindful and involved method that involves some crying. We don’t want you to be afraid because of books like this – we will teach you exactly how to meet your baby’s needs and get the good sleep you and baby deserve.
  6. Price, A. M. H., 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.
    1. This study is one of only a few to look at sleep-trained babies years later. They found that six-year-olds who were sleep trained through controlled comforting or camping out were just as well off as babies who were not sleep trained. In other words, there were no long term effects on attachment or the child’s health. The authors suggest that sleep training often teaches parents to set boundaries and respond to their child’s needs, which is an important skill throughout childhood.
  7. St James-Roberts, I., Roberts, M., Hovish, K., & Owen, C. (2015). Video Evidence That London Infants Can Resettle Themselves Back to Sleep After Waking in the Night, as well as Sleep for Long Periods, by 3 Months of Age. Journal of Developmental and Behavioral Pediatrics, 36(5), 324–329.
    1. This study used video recordings and parent questionnaires to show that babies are capable of self-settling before they turn 3 months old. They found that 5-week-old babies who self-settle when they wake up are probably sleeping longer stretches at 3 months old. The study suggests that self-settling may be a developmental stepping stone that happens before a baby can sleep longer stretches.
  8. Burnham, M. M., B. L. Goodlin-Jones, E. E. Gaylor and T. F. Anders (2002). “Nighttime sleep-wake patterns and self-soothing from birth to one year of age: a longitudinal intervention study.” J Child Psychol Psychiatry 43(6): 713-725.
    1. This study monitored 80 infants from birth to 12 months old and found a few factors that predicted greater self-soothing at 12 months: a) less time outside of the crib in the first year; b) more quiet sleep during the newborn phase; and c) parents taking longer to respond to awakenings at 3 months. 
  9. Ramos, K. D., & Youngclarke, D. M. (2006). Parenting advice books about child sleep: cosleeping and crying it out. Sleep, 29(12), 1616-1623.
    1. This study analyzed 40 books on the market (in 2006) about baby sleep and found that most come from a medical perspective, which supports sleep training (crying with scheduled check-ins). However, there is a substantial minority of books that support co-sleeping and not crying it out.
  10. Kerr, S. M., Jowett, S. A., & Smith, L. N. (1996). Preventing sleep problems in infants: a randomized controlled trial. Journal of advanced nursing, 24(5), 938-942.
    1. This study found that babies whose parents were educated on infant sleep at 3 months old had better sleepers at 9 months than the control group with no education on infant sleep.
  11. Gradisar, M., Jackson, K., Spurrier, N. J., Gibson, J., Whitham, J., Williams, A. S., … & Kennaway, D. J. (2016). Behavioral interventions for infant sleep problems: a randomized controlled trial. Pediatrics, 137(6).
    1. This study split 43 infants into 3 groups for sleep training: graduated extinction, bedtime fading, and no sleep training. They found that both groups of babies with some kind of sleep training were better sleepers at 12 months old than the babies who did not have any interventions. They also found no difference in attachment style or other long-term effects between the three groups.
  12. Kuhn, B. R., & Elliott, A. J. (2003). Treatment efficacy in behavioral pediatric sleep medicine. Journal of psychosomatic research, 54(6), 587-597.
    1. This article analyzed the current research on sleep interventions for children of all ages. The authors concluded that there is still quite a bit of research to be done in the realm of sleep training, although we are off to a good start. In other words, as of 2003 when this study was published, there was no evidence of a clear “best” way to work through sleep problems with children.