Dr. James J. McKenna is a professor of anthropology and the director of the Mother-Baby Behavioral Sleep Laboratory at the University of Notre Dame. He is a world-renowned expert on infant sleep -- particularly the practice of bed sharing in relation to breastfeeding. In our conversations, he shared his insights on co-sleeping and bi-phasic sleep patterns and offered tips for new parents.
You have been supportive of co-sleeping -- describe your research on this sleeping arrangement. In what populations is it common? What are the benefits of co-sleeping?
My research on mother-infant co-sleeping began when we learned that my wife was pregnant. Like most soon-to-be parents, we rushed to buy all the parenting books. But after reading a few books about how best to care for your new baby we were left with one of two conclusions: either everything we had learned in anthropology, my specialty, was wrong, or all these western recommendations about how best to care for babies had nothing to do with babies at all. Maybe it had everything to do with recent western cultural ideologies and social values that more accurately reflect what we want babies to become, rather than who they actually are and what they need.
In any Introduction to Biological Anthropology class, students learn that the human infant is the most vulnerable, contact dependent, slowest developing and most dependent primate-mammal of all, largely because humans are born neurologically premature, relative to other primate mammals. In order for the human infant to safely pass through its mother's small pelvic outlet, which is an architectural requirement to walk upright, the infant has to be born with only 25 percent of its adult brain volume. This means that its physiological systems are unable to function optimally without contact with the mother's body, which continues to regulate the baby much like it did during gestation. Ashley Montagu, my personal intellectual hero, called human infants "extero-gestates." Touching infants changes their breathing, body temperature, growth rate, blood pressure, body temperature, stress levels and growth itself. In other words, the mother's body is the only environment to which the human infant is adapted. As Dr. Winnecott, the famous child psychologist put it, "There is no such thing as a baby, there is a baby and someone."
This is a profoundly true scientific beginning point to understand why babies will never accept nor respond to the memo that says they should sleep alone. The solitary infant sleep environment represents a neurobiological crisis for the human newborn as this micro-environment is ecologically invalid for meeting the fundamental needs of human infants. Indeed, sleeping alone in a room by itself and not breastfeeding are now recognized as independent risk factors for SIDS, a fact that explains why most of the world never heard of SIDS.
My wife and I were shocked when we read what pediatric sleep researchers had to say about normal sleep for human infants and the idea that infants must "self-soothe." Even then we knew this to be no more than a cultural construction without empirical evidence to back up its veracity.
When my son was born, I discovered I could manipulate his breathing by changing the speed of my breath, as if we had to be in sync with each other. My research later confirmed that the breathing of the mother and infant are regulated by the presence of each other -- the sounds of inhalation and exhalation, the rising and falling of their chests, and the carbon dioxide being exhaled by one and inhaled by the other expediting the next breath! I have argued in scientific articles that this is one more signal to remind babies to breathe, a fail-safe system should the baby's internal breathing transitions falter.
I have studied the negative physiological effects of short-term maternal separation on monkey infants -- such as heart rate, breathing, body temperature, susceptibility to viruses, cortisol levels, digestion, and growth itself. How could I be surprised that the least mature primate of all -- us -- is even more sensitive to all sensory signals? Holding, carrying and sleeping with a baby is not just a nice social idea, but also an important contribution to their well-being.
I decided to take my primate behavior knowledge and apply it to ourselves, and to see if nighttime contact (breastfeeding and bed sharing) actually regulated human infants in the ways I described, and what happens when babies sleep alone. I led a team of scientists who for the first time documented the behavioral and physiological effects of solitary infant sleep and what sleep looks like when it is measured in the co-sleeping and breastfeeding context within which it evolved.
We showed how the sensory modalities of mothers and infants mutually affect each other. It's not just the mother changing the infant's sleep and physiological status, but also the infant regulating the mother's behavior and physiological status as well.
It is important to remember that while mother-infant co-sleeping evolved, modern beds and bedding did not. We need to take the needed precautions. But bed sharing can be protective when connected to breastfeeding. We now know that many breastfeeding mothers choose to bed-share precisely because they get more sleep, manage their milk supply better, and attach more intensely with their babies.
When done safely, bed sharing makes mothers (and fathers!) and babies happy and has positive developmental effects on growing children. Surely mothers should not be stigmatized or considered irresponsible for bed sharing. In fact, 90 percent of all human beings sleep with their babies in some form or another!
You have been quoted saying that humans are really bi-phasic sleepers, saying "In America, you are expected to go to bed at 11 o'clock and basically die until 7 a.m., and if you don't, you have a pathology -- insomnia." How do you respond to headlines that put strict boundaries on the amount of sleep we "should" get?
The human metabolism seems to slow down in the afternoon, and, in all probability, our biology is inclined toward some form of bi-phasic sleep. The fact that across diverse cultures most people are able to accommodate this biology no doubt reflects our evolutionary past, having evolved in the tropics where there was a need to get out of the intense heat of the day.
Cultural values underlie, if not regulate, how and when we sleep. In the U.S. the expression, "I don't want to be caught napping," suggests that a nap is some kind of violation. Other cultures, however, favor naps or siestas during the day.
The evolutionary need to be vigilant during sleep and awaken quickly permitted early humans to adapt to changing social, psychological and emotional environmental challenges. It is therefore important to respect individual variability and consider overall health from multiple perspectives. I become uncomfortable when I read these headlines with sweeping statements, which can cause people with more variable sleep patterns to become anxious, especially when they feel great and well-rested during the day. And when all illnesses and syndromes are explained in terms of chronic sleep deprivation, we need to recognize that assessing cause and effect here is very difficult.
As an expert in infant sleep, what tips would you give to new parents to help their child (and themselves) sleep?
Do what works for your family and trust yourself to know your baby better than any external authority. You are spending the most time with your baby, and every baby is different. Infants, children, and their parents intersect in all kinds of diverse ways. Indeed, there is no template for any relationship we develop. When it comes to sleeping arrangements, many families develop and exhibit very fluid notions of where their baby "should" sleep. Parents with less rigid ideas about how and where their babies should sleep are generally much happier and far less likely to be disappointed when their children cannot perform the way they are "supposed to" -- i.e. sleep through the night.
Above all else, keep in mind that babies have no agendas; they are not trying to make it hard on you, or manipulate you. With such an undeveloped little brain, they are about as close to their genes as any human will ever get and have little control over their behavior. In their first six to seven months of life, babies have no "wants," only needs. Keep in mind that babies are as much "victims" of their behavior as you might be.
The key to parents being satisfied is not accepting what others say you must do. Rather, be open to how the constellations of relationships that comprise your family intersect and roll with what solutions seem to work. Try not to judge your infant's sleep. Don't confuse the perceived medical good of sleeping through the night with a "moral good" -- the idea that "good babies" sleep through the night. The worst invention culturally for all parents was the notion of the "good baby."