If there was every a poster child for controversial parenting strategies, the Weissbluth method for sleep training is it. Otherwise known as "graduated extinction" or crying it out, this method has been leaving parents and researchers a like with lots of unanswered questions about the benefits and risks of the Weissbluth method. And like most aspects of parenting, things are rarely black and white — sleep training included.
According to Parenting Science, the purpose of the the cry it out method isn't to teach your child to sleep. It's also isn't meant to be a solution to common sleep problems like separation anxiety, nightmares, fear, snoring, sleep-terrors, or other common problems children have at night. The article stated that the method is designed for "one narrow purpose: to get kids to fall asleep without parental soothing."
However controversial the method may be, it's aimed at helping your child sleep, and the goals certainly aren't to harm your child. But according to the limited research (or lack there of) on the topic, there are definitely a few concerning consequences that are worth taking into consideration before you try out a full-on cry it out method like the Weissbluth.