Cannabis does seem to (maybe) help some people sleep better when they're battling chronic pain or other underlying conditions, but for healthy people, there's no solid evidence that it's a good sleep aid, and the reverse may be true. Not enough research on any of this to state anything with certainty, which is the gist of an article I wrote about it: https://medium.com/wise-well/the-truth-about-cannabis-and-sleep-38a930d3466e