by Lenore Goldfarb, B. Comm, B. Sc., Dip.C., IBCLC


When I say the word “co-sleeping” what comes to mind? Most people automatically think of co-sleeping with their partners or spouses. Next in line is usually a family memory of sharing a bedroom with a sibling.

Dr. Martin Stein (2001) defines “co-sleeping” as “The practice of having an infant or young child share a bed with his or her mother (and often father as well)”. Parent-infant co-sleeping may occur in different formats with different degrees of parental proximity and contact, which may include bed sharing or sleeping on separate surfaces in the same room.(McKenna 1998).

Evolutionary and Cultural Influences on Co-Sleeping:

In our society we think nothing of husbands and wives co-sleeping and mothers routinely ask for “rooming in” sleeping arrangements when they give birth.

James J. McKenna who is a professor of anthropology at Notre Dame University and director of Notre Dame’s Center for behavioral Studies of Mother-Infant Sleep. Has studied Mother-Infant co-sleeping for nearly 20 years. He believes that co-sleeping is what nature intended for us and that evolution has built co-sleeping into our biology (McKenna 1998).

There is anthropological evidence to back this up. Lozoff and Brittenham, in a study published in 1979, gathered data from 186 tropical, non-industrualized societies and found that 100% of the “hunter-gatherer” groups practiced infant-parent co-sleeping. (McKenna 1998). According to McKenna, since these societies are considered to be ecologically and adaptively similar to prehistoric humans, McKenna believes that prehistoric societies also practiced mother-infant co-sleeping in order to protect infants, keep them warm, and safe from predators. (McKenna 1998). McKenna argues that babies are born physiologically expecting maternal touch, smell, sounds, movements and warmth which can only be received by close proximity to their mothers. Depriving a child of these sensations results in the infant survival response of crying. Also, babies are born with just 25 % of adult brain volume making them the least neurologically mature primate species and highly dependent on mother for survival.

In Japan, China, Vietnam, they would not consider sleeping apart from their Children. And in fact Guatemalans find it so difficult to sleep alone that they often seek out other family members or friends to co-sleep.(McKenna 1998).

American children are encouraged to be self-reliant and assert their individuality by sleeping alone. Japanese children are taught to “harmonize with the group” and co-sleep with their parents often until the age of 15. This demonstrates a fundamental difference in attitudes between American and Japanese parents concerning the “nature of the infant at birth” and what sleeping arrangements are necessary to achieve desired developmental and moral outcomes. (McKenna 1998).

McKenna sites a 1971 Barry and Paxton study that found that out of 119 cultures examined around the world, 76 of them practiced co-sleeping. This represented approximately 90% of the world population. By the same token, a survey done in 1984 found that 94% of U.S. pediatricians disapproved of co-sleeping. He also sites a 1985 study by Lozoff et al that found cultural values and medical practice affect each other. The Lozoff study prompted McKenna to do a subsequent study on cultural and scientific influences on co-sleeping. (McKenna 1998).

Reasons for the Prevalence of Mother-Infant Separate Sleeping:

McKenna’s research indicates several potential reasons for the prevalence of mothers and infants sleeping apart. He mentions 17th century laws in Europe that were enacted after numerous impoverished mothers confessed to their priests that they or their husbands had accidentally rolled over on their infants while co-sleeping. This is the origin of the term known as “laying over”. In fact these parents had most likely deliberately smothered their babies when they found they could not provide enough food for them. The laws were designed to stop this infanticide. (McKenna 1998)

In Western cultures such as found in the US there has been a focus on the fear of spoiling the child, and on a desire to make the child more independent. There is a fear that co-sleeping will interfere with marital relations, foster sibling rivalry, start a bad habit, confuse the child sexually or induce over stimulation of the infant. McKenna states that there is no hard evidence to support these concerns. (McKenna 1998). Other concerns are fear that co-sleeping will hinder development of independence, cause more sleep disturbances in parent and child, or that it is physically dangerous for the infant, which McKenna refutes (Stein 2001). In her article Understanding Co-sleeping Mizin P. Kawasaki, MD, lists several myths associated with co-sleeping. Among them are that “co-sleeping is perverse because the marital bed is stigmatized as a den of sin” even though most parents of newborns use their bed primarily for sleeping. Other myths cited include, “children need to sleep alone through the night” and that they are not harmed by forcing them to do so, that “parents should not be inconvenienced by their baby’s needs” during the night, that they “won’t get a good night’s rest with a baby in their bed” and besides, it will somehow “spoil the baby and discourage independence” since once the baby is in your bed it will never leave, and that having the baby there will “interfere with parental intimacy and cause marital discord”. (Kawasaki 2001). A close examination of these myths reveals a strong tendency for the parents to put their needs first and those of their child last. Upon examination of these myths Kawasaki points out that in each and every case there is evidence to refute them.

There is strong cultural pressure to let infants cry themselves to sleep, to put them in their own beds, and refrain from comforting them at night. Harvard Psychiatrist Michael Commons has found that babies who sleep alone are more prone to stress disorders, which can lead to higher cortisol levels in the brain. He suggests that “stressed out babies” are more prone to illness including mental illness and may find it harder to recover from illnesses. (Coburn 2002). McKenna suggests that co-sleeping fosters independence, higher self-esteem, fewer heath problems and better school performance (Coburn 2002). Paul Fleiss, MD points out that babies cry for a reason. They may be hungry, thirsty, sick, uncomfortable, agitated, lonely, frightened or some other reason that we may not be able to figure out. The fact that they are crying in the first place is an indication that they have a problem they cannot solve by themselves and need assistance. He goes on to say that it is unreasonable to expect babies to self soothe and advocates co-sleeping. He says, “If you find that you’re uncomfortable about having your child sleep in your bed, you should examine your own feelings carefully.” (Fleiss 1999).

Co-Sleeping, Safety, and SIDS:

Japan has the lowest rate of SIDS in the world. Japanese babies routinely share their parent’s beds (McKenna 1998).

In 1999 the CPSC put out a report based on research done by Suad Nakumara Ph.D and stating that their own study indicates the practice of co-sleeping is dangerous and accounts for 64 deaths each year from suffocation and strangulation.

La Leche League International responded the next day. (LLL 1999) with a press release which outlined the benefits of co sleeping as follows:

“Studies have shown that co-sleeping with a breastfeeding infant promotes bonding, regulates the mother and baby’s sleep patterns, plays a role in helping mother to become responsive to her baby’s cues, and gives mother and baby needed rest. Co-sleeping... assists mothers with breastfeeding on demand, ....maintaining mother’s milk supply.”

They go on to cite a quote from Dr. McKenna

“we agree with the authors and others that special precautions need to be taken to minimize catastopphoic accidents. However, the need for such precautions is no more an argument against all co-sleeping, and specifically bedsharing, than is the reality of infants accidentally strangling, suffocating, or dying from SIDS alone in cribs, a reason to recommend against all solitary, unsupervised infant sleep.”

He goes on to say that specific hazards of adult beds are not an indication that all bed-sharing is unsafe. McKenna criticized the study because the authors based their findings on incomplete and anecdotal evidence rather than hard scientific data.

McKenna, (2000), Gordon (2000), Sears (2002), Fleiss (1999), Screiber (1999) and others all responded by saying the study was flawed for several reasons. They point out that 90% of SIDS deaths occurred when the baby was alone in its crib. They say that the study wasn’t a valid study and that the recommendations go too far. Assumptions were made based on limited or flawed data which was obstructed by cultural bias, and overlooks proven benefits of co-sleeping, all of which is outlined in detail in McKenna 2000 and Gordon 2000. Rather than ban co-sleeping all together, the authors suggest practicing safe co-sleeping which includes the following:

  • Parents should not co-sleep with their infant if the parents are under the influence of alcohol, recreational drugs, or if they smoke.
  • Parents should not co-sleep with their infant on a soft mattress, couch, water-bed or arm chair as the child may suffocate. By the same token, the family bed should have tight fitting sheets and the mattress should be firm and fit snug up against the wall and care taken so that infant cannot roll out of the bed.
  • Baby’s head should not be covered and infant not be blanketed more than the adults to avoid overheating.
  • Additionally, Parents should avoid wearing garments with long drawstrings or bows that can become undone and pose a strangulation hazard to the infant.
  • Both McKenna and Sears recommend the Arms Reach Co-sleeper as an alternative to bed-sharing when bed-sharing is not a viable option (McKenna, Sears, 1999).

Co-Sleeping and Breastfeeding:

Studies examining infant sleep have been based on infants sleeping in isolation and have not generally taken the method of feeding into consideration. McKenna cites a study by Harper published in 1976 that criticized this. Harper and his colleagues found a difference in REM sleep between breastfed and bottle fed babies. In fact a subsequent study by McKenna (1998) found that co-sleeping breastfed babies are lighter sleepers, have more frequent arousals in sync with their mothers and less incidents of obstructive apnea which all may serve to protect babies from SIDS.

In their book, “Breastfeeding and Human Lactation, Auerbach and Riodan point out that maternal co-sleeping and breastfeeding go hand and hand in that breastfeeding mothers are more likely to co-sleep with their babies than bottle-feeding mothers. They cite the 1997 study by McKenna that proved that infants who co-sleep with their mothers breastfeed twice as often and for three times longer during the night than infants who sleep separately. The study also showed that co-sleeping fosters closer monitoring of the infant . Auerbach and Riodan question whether it is the co-sleeping pattern associated with breastfeeding or the breastfeeding itself that is responsible for lower risk of SIDS. These babies also tend to sleep supine (on their backs) rather than prone (on their stomachs). Co-sleeping increases suckling and encourages more light sleep thus avoiding apnea (McKenna 1998). Co-sleeping mothers continuously “check out” or inspect their babies and adjust their babies’ body positions and blankets throughout the night (McKenna 1994). McKenna also found that mothers and babies tend to sleep face to face. He proposed that the CO2 exhaled by the mother may act as a breathing stimulant for the infant (McKenna 1994).


Mothers who co-sleep with their babies tend to pay more attention to them ... “checking them” out during the night. Babies tend to sleep in the supine position (on their backs) which has been shown by researchers to vastly reduce SIDS deaths. This position also makes mother’s breasts more accessible, which encourages frequent and prolonged breastfeeding. Research has shown that babies who co-sleep breastfeed twice as often and three times longer than solitary sleeping infants which as we all know provides immune benefits. Co-sleeping promotes loving contact, less crying, less sleep disturbance. Mother and baby’s breathing become somewhat coordinated as does their arousal patterns. Mother’s and babies tend to sleep “lighter” and so mom can sense if there is a problem with the baby. Baby’s who sleep lighter are mostly likely at further reduced risk of SIDS.

Some additional resources:

The evidence provided by Dr. McKenna suggests that co-sleeping is a sound practice with valuable benefits. Dr. William Sears provides witness to many of the benefits of co-sleeping, found by McKenna’s research, which he outlines on his website in an article entitled “Co-sleeping: Yes, No, Sometimes?’ (2002) and in his book “Nighttime Parenting’.

Another first hand account may be found in the book “The Family Bed’ by Tine Thevenin who is a long time La Leche Leader.

These authors provide guidance for co-sleeping and address concerns such as the effect on marital relations as well as the child’s natural tendency to become more autonomous as they develop and eventually gravitate to their own space as they become older.



Cosleeping (Bedsharing) Among Infants and Toddlers by Martin T. Stein MD, Calvin A. Colarusso MD, James J. McKenna Ph.D., Nancy G. Powers, MD, 
Journal of Developmental and Behavioral Pediatrics, April, 2001

Cultural Influences on Infant and Childhood Sleep Biology, and The Science that Studies It: Toward a More Inclusive Paradigm by James J. McKenna, Ph.D, 
This article was published in Sleep and Breathing in Children: A developmental Approach, pub. Marcell Dakker 2000, pages 199-230

Co-Sleeping: Yes, No, Sometimes? by William Sears, MD, 
Ask Dr., Feb. 18, 2002

Co-Sleeping Another Way to Promote Infant Health by Jennifer Coburn, 
San Diego Breatfeeding Coalition, 2002

Understanding Co-sleeping by Mizin P Kawasaki, MD, 
Human, 2001

Pillow Talk: Helping your Child Get a Good Night’s Sleep, by Paul M. Fleiss, MD, 
Mothering Magazine, Issue 96, Sept./Oct. 1999

CPSC Warns Against Placing Babies in Adult Beds; Study finds 64 deaths each year from suffocation and strangulation by U.S. Consumer Product Safety Commission, 
Sept. 29, 1999, Release #99-175

Solutions to Infant Overlayment Deaths in Parent’s Bed Recognized by Experts; Arm’s Reach Concept’s Bedside Co-Sleeper (tm) Endosed by James J, McKenna, Ph.D. and Dr. William Sears. 
PR Newswire Oct. 27, 1999

A Reply to the Consumer Product Safety Commission Statement on Co-Sleeping by David Servan-Schreiber, MD., Ph..D, 
The Family Bed Page, Sept. 30, 1999

In Defense of the Family Bed by David Servan-Schreiber, MD, Ph.D, 
The Family Bed Page, Sept. 30, 1999

In Defense of Infant-Mother Cosleeping. (Brief Article) (Statistical Data Included), by James J. McKenna, Ph. D., 
Mothering, Jan-Feb. 2000

Co-Sleeping and Suffocation: A Response to the Consumer Product Safety Commission Study by Attachment Parenting International, 
API News, June 2000

Apnea and periodic breasthing in bed-sharing and solitary sleeping infants by Christopher A. Richard, Sarah S. Mosko, and James J. McKenna, 
Journal of Applied Physiology, vol 84, Issue 4, pp 1374-1380, April 1998

Experimental studies of infant-parent co-sleeping: mutual physiological and behavioral influences and their relevance to SIDS (sudden infant death syndrome) by James McKenna, Sarah Mosko, Christopher Richard, Sean Drummond, Lynn Hunt, Mindy B. Cetel, and Joseph Arpaia, 
Early Human Development 38 (1994) pp 187-201


Kathleen Auerback and Jan Riordan: Breastfeeding and Human Lactation, 2nd ed. Pub Jones and Bartlett, 1998, p. 660

William Sears, MD : Nighttime Parenting, pub by La Leche League Inernational, 1999

Tine Thevenin: The Family Bed, pub. Avery Publishing Group, 1987