http://www.examiner.com/article/study-shows-babies-who-cry-it-out-remain-stressed
A new study offers more reason not to practice “crying it out” with babies.
Researchers at the University of North Texas monitored the cortisol levels of crying babies and their mothers over five nights when the infants were undergoing sleep training in order to learn to “self-settle.”
The researchers found high levels of cortisol, a stress hormone, in both the mothers and the babies during the times the babies were crying. After several days, the babies learned to go to sleep without crying.Researchers found that during these quiet nights, the mothers no longer had high cortisol levels but the babies’ cortisol levels remained high. They had merely learned to remain quiet while distressed. (click link above to read the article)