When the child is under 6 months you probably don&#x27;t want to delay when the child is crying.  Under 6 months they cry to communicate a need - they&#x27;re hungry; they need changing; they&#x27;re in pain; they&#x27;re cold&#x27; they&#x27;re lonely.<p>Most people think it&#x27;s a good idea to address those needs.<p>Even the people who like sleep training think you probably shouldn&#x27;t start when the child is under 6 months.<p>There are a couple of people who think you can start sleep training under 6 months (Ferber; Gina Ford), but even Ferber sets a minimum age of 4 months.<p>If you are going to go down the &quot;cry it out&quot; route you will want to carefully investigate the different systems.  Some of them have been discredited as harmful and cruel.  Ferberization (or Gina Ford, they&#x27;re pretty similar) is about the harshest system that a modern parent could get away with, but you need to be aware that a lot of people <i>hate</i> this method.