The Nurture Revolution: Grow Your Baby's Brain and Transform Their Mental Health through the Art of Nurtured Parenting

by Greer Kirshenbaum

In other words, while some babies are indeed quiet in their cribs after they’re sleep trained, we know that nothing has actually changed in their development, so those babies are still waking, and still in stress, but they know that no one is coming to co-regulate them, so they stop bothering to signal for help. This process uses babies’ innate survival mechanism to shut down if no one is around to help. Instead of entering sleep through a safety state, they enter through a fearful stress state. Sleep training puts the infant brain at risk of experiencing high and/or prolonged periods of toxic stress. It puts the infant brain at risk of developing a highly reactive amygdala and hypothalamus, with a diminished ability to regulate stress via lower stop signals in the hippocampus and prefrontal cortex. There is likely a spectrum of how babies are affected by this experience. It’s not a deterministic risk, as genetics and experience certainly contribute—genetics might be protective for some babies and increase vulnerability for other babies. Sadly, it’s often vulnerable, highly reactive babies who need the most co-regulation—and thus wake the most at night—who are likely to be sleep trained.