I would encourage all new parents and those considering children to read this article. Having your baby "cry it out" is a modern practice and we are now starting to see it's unfortunate effects. Here are a few choice paragraphs:
"With neuroscience, we can confirm what our ancestors took for granted---that letting babies cry is a practice that damages children and their relational capacities in many ways for the long term. We know now that letting babies cry is a good way to make a less intelligent, less healthy but more anxious, uncooperative and alienated person who can pass the same or worse traits on to the next generation.
The discredited behaviorist view sees the baby as an interloper into the life of the parents, an intrusion who must be controlled by various means so the adults can live their lives without too much bother. Perhaps we can excuse this attitude and ignorance because at the time, extended families were being broken up and new parents had to figure out how to deal with babies on their own, an unnatural condition for humanity--we have heretofore raised children in extended families. The parents always shared care with multiple adult relatives...
The fact is that caregivers who habitually respond to the needs of the baby before the baby gets distressed, preventing crying, are more likely to have children who are independent than the opposite(Stein & Newcomb, 1994). Soothing care is best from the outset. Once patterns get established, it's much harder to change them.
We should understand the mother and child as a mutually responsive dyad. They are a symbiotic unit that make each other healthier and happier in mutual responsiveness. This expands to other caregivers too."