http://www.askdrsears.com/html/10/handout2.asp
Science tells us that when babies cry alone and unattended, they experience panic and anxiety. Their bodies and brains are flooded with adrenaline and cortisol stress hormones. Science has also found that when developing brain tissue is exposed to these hormones for prolonged periods these nerves won’t form connections to other nerves and will degenerate. Is it therefore possible that infants who endure many nights or weeks of crying-it-out alone are actually suffering harmful neurologic effects that may have permanent implications on the development of sections of their brain? Here is how science answers this alarming question.