There were no comparison groups included in the study to validate such a conclusion – no infants lounging around at home with much lower cortisol levels – so it's unfair to assume that the sleep-trained infants were stressed.
(Middlemiss told me that she once took cortisol measurements of babies while they were at home, and that their cortisol levels were lower than the babies tested in the sleep lab, but she didn't include this information in her study.) Even if the babies at the sleep lab were highly stressed, the obvious take-home is that parents shouldn't bring their babies to sleep labs – not that they shouldn't cry it out.
Another word that gets thrown around a lot when people talk about sleep training is “attachment.” Attachment is an extremely misunderstood concept; basically, it describes a child's relationship with his mother or father as it develops over the course of the first year of life. A child who is securely attached to his mother is confident that she is there for him, because she has been repeatedly and appropriately responsive to his cues and needs. A child who is not securely attached is not so sure mom can be counted on, because she has been unpredictable in her responsiveness or perhaps even abusive. Securely attached children go on to have stronger relationships throughout life and are more confidant, cooperative, caring and emotionally stable than those who aren't securely attached totheir caregivers. Attachment is powerful – no question – and important.
But attachment isn't extremely fragile, nor is there a formula parents need to follow to ensure that it develops.
“Don't get me wrong: I think nursing is great for lots of reasons, co-sleeping is fine, and carrying a baby in a sling is great, but you can do all of those things and not be a sensitive parent,” says Alan Sroufe, a professor emeritus at the University of Minnesota Institute of Child Development, who has studied attachment for decades. And no, you won't threaten a secure attachment with your baby if you let her cry at night a few times, either: Sroufe let his own daughter cry it out for a few days when she was about 8 months old. (It worked.)
“Did I think she would be traumatized by this? No. This business of being sensitive and responsive – it's about being sensitive and responsive the vast majority of the time,” he says. (Sroufe believes, however, that crying-it-out is inappropriate for younger babies; some researchers have drawn a “safety” line at 6 months of age because that's when infants develop object permanence, the ability to understand that mom and dad still exist when they're not visible.)
But what if it takes weeks of intense crying, night after night, to sleep train your child?
Days, not weeks
Here's the thing: When crying-it-out is done properly, the experts say, it doesn't take weeks. It takes days. In Middlemiss' study, the babies stopped crying by the third night. A 1988 trial also reported significant improvements in infant sleep within three days using the method. Yet we've all heard horror stories about parents who have had to endure weeks upon weeks of all-night screamfests.