Is Sleep Training Helpful or Harmful?

Whenever I hear the words sleep training, I feel a little uncomfortable. Although I do not know much about the various methods of sleep training, it always seemed to me that letting a baby “cry it out” was cruel and potentially harmful. To become better informed, I listened to a presentation on the subject by Tracy Cassels, Ph.D. Dr. Cassels presented the science on sleep training, thoroughly examining the available research on the subject.

This is what I gleaned from the presentation:

-Many of the studies in support of sleep training suffer from poor methodology, thereby undermining the results.

-Many rely on parent report, which is notoriously inaccurate when the perceived intervention has been deemed to be helpful.

-Sleep training does not improve infant sleep. Babies do not sleep longer or better. Sleep-trained babies continue to awaken at night, and they do not cry for parental attention when they do.

-Infant and child-waking at night is normal. Parents have often been led to believe that it is not.

-Night-waking does not undermine proper cognitive development.

-Sleep training is stressful for both babies and their parents.

As a developmental psychologist, I feel most disturbed by the latter issue. Sleep training causes stress in the baby increasing cortisol levels. Extinction of the crying during sleep training does not decrease stress levels. Babies will continue to experience heightened stress and cortisol levels, even when they are not crying. We have known for some time that chronically elevated cortisol levels negatively affect the developing brain. Add to that the interruption of parent-child synchrony and co-regulation, the risk of long-term emotional regulation difficulties becomes very real.

I have hit just the highlights here. If you have ever been asked to help a parent with their sleep concerns, this presentation is a must-see. You can learn more at and see her presentation at