One of the (many) repercussions I noticed with our baby when we were in the midst of the sleep training process was that she oscillated between extremely clingy, and incredibly distant throughout the day.
Sleep training had taught her that she needed to hold on for dear life when she knew separation was headed her way (for example, before naps and bedtime), and to protect herself from further emotional distress when we were reunited (when we picked her up from her crib after the night or nap training). ⠀⠀⠀⠀⠀⠀⠀⠀⠀
It was heartbreaking. We finally woke up to the reality that we had been following the advice of an ‘expert’ who didn’t care to understand our baby’s temperament, instead of following our instincts. We then had to spend a great deal of time repairing our relationship with her, gaining her trust back, and showing her that she could depend on us. ⠀⠀⠀⠀⠀⠀⠀⠀⠀
Though there is no humane way of studying the psychological effects sleep training may have on babies, I can tell you from my personal experience that my baby has grown to be a beautiful, smart, capable – and incredibly anxious – little girl. She may have found herself to be an anxious person regardless of what we did. But neither of her brothers were sleep trained, and neither have the kind of separation anxiety she does. ⠀⠀⠀⠀⠀⠀⠀⠀⠀
The point is, we just don’t know. What we do know – and what has been studied – is the effects of emotional support and secure attachment on children. And since sleep is the most vulnerable state a child experiences – I think it is prudent to be careful not to risk upsetting the secure attachment a child needs to develop with his or her parent.