Kellymom's thoughts on CIO

From the Kellymom website;

What about letting baby ‘cry it out’?

There are two schools of thought about getting babies to sleep. One is a rather rigid method of "sleep training" where a baby is put down awake in a crib and left to cry himself to sleep so that he learns to "self-soothe" and doesn't develop sleep associations that require someone else to put him to sleep. This method has been around since the 1890's and was dreamed up by male university sleep laboratory researchers. Many of the popular "sleep training" methods of today are modified versions of this (allowing baby to cry for progressively longer periods without comforting him, instead of just leaving him to cry until he gives up and stops).
I can't, with good conscience, recommend the cry-it-out method for getting baby to sleep. Anyone who advises you to let your baby cry until he gives up and falls asleep is focusing on the baby's behavior (going to sleep by himself) and not on how the baby feels in the process. In my opinion, this "sleep training" often creates an unhealthy attitude about sleep: after going through this training, baby tends to view sleep as a fearful state to enter into and to remain in. Parents often need to "retrain" baby if there is any break in the usual routine. In addition, it can condition parents to ignore baby's cries, and break down the relationship of trust between parent and child.
Younger babies, in particular, do not have that sense of "object permanence" and if mom leaves them to cry, they are developmentally *unable* to realize that she is just in the next room. All baby knows is that he has been abandoned and that mom is not there. A young baby can only express his needs through crying. A baby who is left to cry alone will eventually stop crying because he has abandoned all hope that help will come: as far as he can tell, no one cares enough to listen, or come and provide comfort. In the book Our Babies, Ourselves: How Biology and Culture Shape the Way We Parent, anthropology professor Meredith Small writes, "When signals are missed, babies stop signalling; they withdraw; they suck their thumbs; they turn away; they try to right the system themselves by not sending out any more signals." The baby protects himself by shutting down, and "accepts" the situation because he has learned that a response is not forthcoming. Crying is also hard, physically, on baby: it can lead to hoarseness that can last for days; the digestive system is upset; heart rates can climb to levels over 200 beats per minute; and oxygen levels in the blood are diminished.
Another school of thought, which I subscribe to, discourages viewing sleep as a state you can *force* a baby into. Instead, it's best to create a sleep-inducing environment that allows sleep to overtake the baby. The process of breastfeeding itself regulates baby's temperature and heart rate and lowers his blood pressure, and puts him to sleep. This helps your baby develop a healthy attitude about sleep, where baby views sleep as a safe, comforting, natural state.

http://www.kellymom.com/parenting/sleep/comfortnursing.html