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Many people choose to co-sleep with their children because of supposed psychological and sleep quality reasons. Are there any scientific studies or other concrete evidence to back them up?

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I lost a 4 month old grandson because his mother rolled over in her sleep with the baby in the bed. The death was ruled accidental asphyxiation. Be very careful about sleeping with very young children. You don't want to go through the aftermath. –  Bill Apr 28 '11 at 20:57
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@Bill - I'm sorry for your loss. I think that statistically, this is rare, and is usually related to alcohol or drug use (perscription, OTC, or illegal), or to improper bed setup for an infant. But that discussion should take place elsewhere. I think that asking about the risks of co-sleeping and statistics around it would be a great question. I would recommend that you ask the question. –  Javid Jamae Apr 28 '11 at 21:54
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This is an excellent question, and it's a shame that there's not really a decent answer linking to quality studies. –  DanBeale Sep 15 '11 at 10:00
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@DanBeale I'm adding a bounty on it to attract some new attention. Hope it helps! –  Torben Gundtofte-Bruun Sep 28 '11 at 7:39
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@Bill So sorry for your loss. My friend's 4 month old also died while co-sleeping with her with no drugs, etc involved. The risk is so great and the consequences unspeakable. –  Marie Hendrix Sep 29 '11 at 10:34
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9 Answers

up vote 18 down vote accepted
+100

The short answer to "is there any scientific evidence in favor of co-sleeping?" appears to be "yes".

TLDR version: There are studies, particularly by Professor James McKenna, that show that there are strong correlations between co-sleeping and improved breast feeding. These same studies suggest that co-sleeping mothers get at least as much sleep as mothers who sleep apart. However, there is considerable controversy over the impact of co-sleeping on SIDS. There is evidence supporting both the idea that co-sleeping reduces factors associated with SIDS, and that proper co-sleeping practices (there is no doubt that improper co-sleeping practices are associated with strong risks) have possible correlations with an increase in SIDS. Neither side has any conclusive evidence, though. /end TLDR

There is a lot of speculative theories, and little in the way of concrete scientific research that I could find.

The most notable research seems to be that of Professor of Anthropology James McKenna. He has conducted research on mother-infant pairs in a laboratory environment, monitoring their sleeping habits as they slept both apart and together over three consecutive nights.

I am not certain if the "three nights" were were three each of apart and together, or 2 of one and one of the other. I also cannot find information about the normal sleeping habits of those mother-infant couples, as it would seem that disruptions in their standard sleeping arrangements would bias the results (i.e. mothers who normally co-slept at home would likely show less favorable results when sleeping apart in a laboratory environment, and vice versa).

The concrete portions of the research seem to be summarized here:

We found that bed-sharing infants face their mothers for most of the night, and that mother and infant are highly responsive to each other's movements, wake more frequently, and spend more time in lighter stages of sleep than they do while sleeping alone. Bed-sharing infants nurse almost twice as often, and three times as long per bout, as they do when sleeping alone. But they rarely cry. Mothers who routinely sleep with their infants get at least as much sleep as mothers who sleep without them.

However, Professor McKenna has extended this research with some speculative theories:

In addition to providing more nighttime nourishment and greater protection, sleeping with the mother supplies the infant with a steady stream of sensations of the mother's presence, including touch, smell, movement, and warmth. These stimuli can perhaps even compensate for the human infant's extreme neurological immaturity at birth.

Co-sleeping might also turn out to give some babies protection from sudden infant death syndrome (SIDS), a heartbreaking and enigmatic killer. Co-sleeping infants nurse more often, sleep more lightly, and have practice responding to maternal arousals. Arousal deficiencies are suspected in some SIDS deaths, and long periods in deep sleep may exacerbate this problem. Perhaps the physiological changes induced by co-sleeping, especially when combined with nighttime breastfeeding, can benefit some infants by helping them sleep more lightly. At the same time, co-sleeping makes it easier for a mother to detect and respond to an infant in crisis.

He goes on to emphasize the speculative nature of the comments on SIDS:

The effect of co-sleeping on SIDS remains to be proved, so it would be premature to recommend it as the best arrangement for all families. The possible hazards of co-sleeping must also be assessed. Is the environment otherwise safe, with appropriate bedding materials? Do the parents smoke? Do they use drugs or alcohol? (These appear to be the main factors in those rare cases in which a mother inadvertently smothers her child.)

However, there are also studies that show a correlation between co-sleeping and an increase in the rate of SIDS.

The American Academy of Pediatrics doesn't recommend completely against co-sleeping, but rather suggests restrictions and conditions:

  • Infants should not be put to sleep on waterbeds, sofas, soft mattresses, or other soft surfaces.
  • Bed sharing or cosleeping may be hazardous under certain conditions.54113–115

    • As an alternative to bed sharing, parents might consider placing the infant's crib near their bed to allow for more convenient breastfeeding and parent contact.

    • If a mother chooses to have her infant sleep in her bed to breastfeed, care should be taken to observe the aforementioned recommendations (nonprone sleep position, avoidance of soft surfaces or loose covers, and avoidance of entrapment by moving the bed away from the wall and other furniture and avoiding beds that present entrapment possibilities).

    • Adults (other than the parents), children, or other siblings should avoid bed sharing with an infant.*
    • Parents who choose to bed share with their infant* should not smoke or use substances, such as alcohol or drugs, that may impair arousal.

The AAP also cites some studies that have shown a correlation between co-sleeping and SIDS. In some cases this correlation appears to be influenced by known factors (maternal smoking, co-sleeping on a sofa instead of a bed, drug or alcohol use by the parents, etc.), but in others seems only linked to the infant's age:

epidemiologic studies of bed sharing have shown that it can be hazardous under certain conditions. Several case series of accidental suffocation or death from undetermined cause suggest that bed sharing is hazardous. 34,37–39 A number of case-control studies of SIDS deaths have investigated the relationship of SIDS with parent(s) and/or other adults or children sleeping with an infant. Some of these studies have found the correlation between death and bed sharing to reach statistical significance only among mothers who smoked. 41,47 However, the European Concerted Action on SIDS study, 42 which was a large multisite study, found that bed sharing with mothers who did not smoke was a significant risk factor among infants up to 8 weeks of age. Similarly, a more recent study conducted in Scotland48 found that the risk of bed sharing was greatest for infants younger than 11 weeks, and this association remained among infants with nonsmoking mothers. The risk of SIDS seems to be particularly high when there are multiple bed sharers 31 and also may be increased when the bed sharer has consumed alcohol or is overtired. 42,47 Also, the risk of SIDS is higher when bed sharing occurs with young infants. 40–42 It is extremely hazardous when adults sleep with an infant on a couch. 31,40,41,48 Finally, the risk of bed sharing is higher the longer the duration of bed sharing during the night.

The same paper from the AAP does mention studies that indicate benefits to co-sleeping:

electrophysiologic and behavioral studies offer a strong case for its effect in facilitating breastfeeding and the enhancement of maternal-infant bonding.

The studies referenced in that quote are two of McKenna's:

  1. Mosko S, Richard C, McKenna J. Infant arousals during mother-infant bed sharing: implications for infant sleep and sudden infant death syndrome research. Pediatrics. 1997;100:841– 849
  2. McKenna JJ, Mosko SS, Richard CA. Bedsharing promotes breastfeeding. Pediatrics. 1997;100:214 –21

McKenna and his associates have issued a rebuttal to the AAP recommendations, specifically regarding co-sleeping.

Most studies have shown no increased risk from infants bedsharing with non-smoking mothers, though the large multicentre European study showed a small risk, and a Scottish study showed a larger risk, particularly for younger infants, though no account was taken of parental alcohol intake. ... Clearly there are inappropriate circumstances or environments in which co-sleeping occurs, with increased vulnerability of some infants, and these deserve further investigation. Over the last three years we have been investigating all unexpected infant deaths in the southwest of England (population 5 million), approximately half of whom were co-sleeping with a parent. The vast majority (>90%) of these co-sleeping deaths occured in an unsafe co-sleeping environment as defined by current UK guidelines ... After thorough death scene and postmortem investigations we have no evidence that the few SIDS deaths that occurred in a relatively safe co-sleeping environment are more than would have happened if the infants had slept alone in cots. ... Changing current guidelines to advise against co-sleeping for this particular group of mothers [non-smoking] would seemingly have little if any effect on the SIDS rates but could deny these mothers and infants any potential advantages in co-sleeping, including accessibility to the breast.

He goes on to emphasize some of the potential benefits of co-sleep, and explains the difficulty in providing epidemiological evidence:

[Bedsharing] is accepted as normal human practice by anthropolgists and infant physiologists. Indeed, much research has been conducted into mother-infant interactions, skin-to-skin care (Kangaroo care), arousal patterns, and the architecture of infant sleep. These studies are often conducted on small selected populations and because of the complex issues involved are more qualitative than quantitative, but are necessary to derive a balanced argument on the potential benefits of bedsharing. While many studies have shown a positive correlation between bedsharing and breast feeding, the lack of conclusive evidence that bedsharing has a causal role in the establishment and continuation of breast feeding may be a reflection of the lack of appropriate studies rather than the lack of such an effect.

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This is a very well-thought-out answer, I want to upvote it again. –  Sarato Sep 28 '11 at 14:53
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This is an excellent, well-researched answer! –  Tyler Holien Sep 29 '11 at 13:51
    
Just like a magazine or well-written blog, a full article can gain readers from a TLDR version, or what's commonly known as an 'introduction.' Yours worked on me, well done. –  monsto Oct 2 '11 at 18:19
    
WOW! and Torben says I'm thorough! I also read in THE BABY BOOK by Dr. Sears, that when comparing rates of SIDS in countries where mothers traditionally co-sleep with rates of SIDS in countries where babies traditionally sleep separately, SIDS occurs more in the separate sleeping countries (but there really could be Many factors influencing those trends other than just sleeping practices) –  balanced mama Dec 11 '12 at 2:26
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A quick search will yield many articles and studies that show infants benefit from touch. With co-sleeping, infants are touched while falling asleep and often all through the night. Among other things, touch helps to increase the parent-child bond.

Parents get much better sleep because they don't usually have to get up and fully wake if the baby wakes during the night. Babies get better sleep because they don't have to wait for a parent to come get them for feeding. Note that this isn't just being lazy; well-rested parents can better care for their child during the day.

According to pediatrician Dr. William Sears, a leading proponent of attachment parenting (of which co-sleeping is a fundamental part), falling asleep in the arms of a parent helps infants learn that going to sleep is pleasant. It also helps to establish trust and reduce separation anxiety.

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why does it reduced seperation anxiety? doesn't that sound counter-intuitive? –  tenpn May 17 '11 at 8:01
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I agree with nearly all of your answer, except that my personal opinion on "well-rested parents" is that I'm a lot more rested when I don't hear all the inconsequential movements and sounds. Having my son in the next room (with the doors open) adds just enough "noise-reduction" filter so that I do hear and react to anything that's more than inconsequential. Between that, I sleep better. But maybe it's just me. –  Torben Gundtofte-Bruun May 17 '11 at 14:22
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@tenpn I believe Dr. Sears is referring to nighttime separation anxiety. You're still there when baby wakes during the night, so baby doesn't learn to fear falling asleep. By the time they transition to their own beds, they're usually old enough to understand that mom and dad are close by. –  Tyler Holien May 26 '11 at 17:11
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@tenpn - It does sound counter-intuitive, but the basic premise around attachment parenting in general is that the parent is able to readily meet the needs of the baby, including the need for touch, food, and security. Once the baby gets older, it's ingrained that these basic needs will be met, and so the child has more confidence. There's more info than what I can put in a comment, but if you're interested in more, check out attachment parenting, as well as Maslow's Hierarchy of Needs (for a foundation of some of the principles of AP). –  Shauna Jun 20 '11 at 14:18
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Quite frankly, I don't understand why this answer has so many upvotes. The question is asking for scientific evidence. Saying that a google search shows that lots of people think co-sleeping is a good idea doesn't actually answer the question at all. –  Beofett Sep 29 '11 at 2:28
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I don't know about scientific studies, although I'm sure there are, but for us the main reasons is that we like to be all in the same big bed and in the beginning this enables us to respond to our child's needs without waking completely and getting up.

If I remember correctly for newborns scientific studies have shown that for non-smoking and non-alcoholic parents, co-sleeping reduces the likelihood of SIDS (Suddent Infant Death Syndrome).

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It's called SIDS because we don't know what causes it. No one knows that co-sleeping reduces it, either, only that there is a slightly lower proportion of SIDS cases in co-sleeping families. Correlation is NOT causation. There could easily be some other factor common among co-sleeping families that effects SIDS rates. Otherwise, good advice (re: not waking completely when caring for baby). –  HedgeMage Apr 6 '11 at 20:57
    
@HedgeMage: you're of course right that correlation is different from causation. Still it does kind of makes sense to me that if you sleep right next to your child you'll be able to respond more quickly and effectively to any distress, unless of course you inadvertedly do harm to him/her while sleeping. But no proof of that... –  inovaovao Apr 7 '11 at 21:47
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@HedgeMage - While I do agree that SIDS is just a fancy name for "we don't know," there is evidence that one of the "causes" of SIDS (ie - one of the things that's happening that is currently ruled as SIDS) is sleep apnea. Basically, the child's system "forgets" to breathe while asleep because it can sleep deeper, but isn't developed enough yet to "remember" to breathe while in deep sleep. Dr. Sears addresses this and his studies have suggested that co-sleeping helps reduce the number of apnea episodes in infants, which is where the "SIDS reduction" comes from (at least, what I know of). –  Shauna Jun 20 '11 at 14:12
    
@Shauna By any chance do you have any links to any of Dr. Sears' studies? I'm very interested in seeing the research he has done, but I have been unable to find any details of his studies other than his results. –  Beofett Nov 29 '11 at 20:32
    
Beofett - Not offhand, sorry. He does have connections with Harvard Medical School and the University of California, so if you have access to academic journals and the like, you might have luck finding the original studies there. –  Shauna Nov 30 '11 at 14:44
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To point out from the start I have no links to corrobarative information. BUT, I am here as I am looking for the same thing.

I am a single father and get my kids 50% of the time. I co slept with my sone from day 1 and he is now 5 and a dream to be around. My daughter, due to lack of room in the bed was in a crib at the foot of the bed. She had tantrums, and screaming. This is not scientifically measured but my gut feeling as a parent that co sleeping makes them calmer. I co slept with my parents and have wonderful memories waking up on a saturday morning and my dad making everyone a cup of tea to drink jn bed (one of those Tea s Maids bedside things from the 70s).

I am literally hunting for advice and information on SCIENTIFIC studies on either side of the argument as it seem the only bad things people bring up are SIDS which is not SCIENTIFICALLY proven to be relative. As some people have said, without a scientific study it is purely opinion and hearsay. Nothing more.

The only information I have found online is this: http://www.timesonline.co.uk/tol/news/uk/article1083020.ece

It 'mentions' studies but does not link to reference them.

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I would like to point to sociological evidence as a scientific equivalent, just as Hannibal related the study of African mothers. When my wife and I were adopting we were exposed to a lot of material about social norms in other countries with respect to child rearing practices. We were shocked to find out that Caucasian American/Canadian and most families of Anglo-Saxon decent are the only families that don't practice some form of co-sleep and "baby carry". They basically told us that even if the infant did not co-sleep, the family dynamic is such that babies and toddlers almost always sleep in the same room as siblings or parents. This "structure" and bond has a lasting impact on the children in those societies. I don't know the reason why it is so different in the United States, but I suspect there is some merit to this practice in other countries.

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I notice that many people have stated that not having to wake completely to nurse is a major benefit. I am a bit baffled by this being such a strong argument for co-sleeping for a number of reasons:

  1. Nursing a newborn was not that easy for me, perhaps because I am very large chested and there was a constant danger of suffocating my daughter while feeding her (I suppose this is not a universal issue.)
  2. I rarely fully woke up while nursing my daughter at night - her crib was in our room and so was a place for me to sit.
  3. Generally the part that did require waking up was the need of a dry or clean diaper - I do not understand how co-sleeping assists in this.

This question prompted me to do some research and I found that there are studies that will "prove" that either way is better. This leads me to believe that there is no real evidence either way. Personally the chance, no matter how small, that I might smother my child is enough that I will not co-sleep with her. The death of a baby would be devastating regardless, but the guilt and self anger that would come with smothering my own child would be unbearable (I am assuming).

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-1: Doesn't answer the question. –  Javid Jamae Sep 23 '12 at 20:15
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Well.

I studied psychology and let me tell you of a story. A research that was done in later years.

There was a compare of an African tribe and an American family of sleep orders.

Of course as with everything in psychology this is really a far fetch thing.

The study was about this:

The African mothers carry there children around in a bag around there body until they are 3. They sleep with the child, they work with the child, they are constantly with the child. When they sleep the child hears the heart beat of the mother constantly.

Then when they turn three they put them down, and never ever take them up again. The child however is so self confident and so self aware that it has no problem at all sleeping alone and with being alone as he has the most reassuring though that his mother will always be there.

Now... psychology tells us many things...And this study is of course a bit extreme since you can't compare an African tribe to an American family...

You can sleep with your child. But not for to long. Why? Because he needs to know that there is a place of his own. But than again, how old is the child? Mostly parents are just lazy. They don't want to wake up, walk to the child's room and nurse him there. It's inconvenient.

When sleeping with a child you first develop confidence in him that you are around. But be careful not to over do it. Because children get used to stuff really quickly. And then you end up having an unhealthy relationship with him. And that he can't do anything on his own, because he needs his parents to be with him. And he can't sleep well because his system depends on the nearness of his parents.

So.. :)

Summary is:

You can of course co-sleep. Studies show that it helps until a certain amount of time. And you can better watch your child breathing normally too, like the previous answer stated.

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Corroborative links please, otherwise your answer is just hearsay. –  Jon Hadley Mar 31 '11 at 19:21
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I have no idea what so ever since it was in one of my psychology books about 6-7 years ago. I don't care what you vote for me, i just want to give sound advices. And if the guy how asked the question found it useful.. then i will die a happy man. :) –  Hannibal Mar 31 '11 at 19:37
    
I'm sorry that may have sounded a bit harsh. Fact is, i don't have a link to prove it. I'm sorry about that. –  Hannibal Mar 31 '11 at 19:51
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http://www.naturalchild.org/james_mckenna/cosleeping.pdf

See this link for an excellent article backed by scientific research.

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-1 for just posting a link. It's good practice to also post a summary or the most useful excerpt along with the link. I'll remove my downvote if you do that :-) –  Torben Gundtofte-Bruun Nov 29 '11 at 20:28
    
Just in case the link source goes away it is nice to sum up the important points made by the article. It also helps a viewer of your answer know if they'd like to go read more if you include a quick description of what will be found if the viewer follows the link. –  balanced mama Nov 8 '12 at 2:58
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I have an opposing viewpoint, hopefully not too controversial, but hopefully valid as it has been the same with all 3 of my children:

Co-sleeping ruins the parents' sleep - children continually move at night and there is no way to get a good sleep with them! It also discourages them from being happy wherever they sleep - which can make holidays more fraught.

I am all for having them in a cot in the same room for the first few months, but then pop 'em into another room to get some peace and quiet on both sides, you and them. After about 12 months you need to be rationally looking at what doesn't impact your lives too much - if you have a routine, children will fit in easily, whereas changing your own routine to fit theirs just makes life difficult! Especially when you want to have them babysat by the in-laws or friends!

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@Roy do you have experience with co-sleeping, or are you making an assumption? –  David Apr 7 '11 at 22:29
    
My experience was the opposite -- sleeping with the child made it so she could nurse in the middle of the night without having to wake up either me or my wife, so we all got a lot more sleep. –  Gabe Apr 8 '11 at 7:04
    
@David - yep, experience with the first 2. We didn't bother with the third as it was way too tiring! –  Rory Alsop Apr 8 '11 at 7:57
    
I disagree, my sleep improved once we realised co-sleeping was an option and it has stayed fine since more children have arrived. We have another child soon to arrive and we'll see how that goes, but in my experience, we have better sleep with them, rather than without them in the bed. One aged 8 still climbs in occassionally; once they not longer want to, they'll not do it. –  Hairy May 17 '11 at 11:16
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Rory, your answer misses the point. Javid was asking for scientific evidence in favor, and you provided none. Sorry, but I have to -1 that even though I agree with what you're saying. –  Torben Gundtofte-Bruun May 17 '11 at 14:25
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