According to some videos in which Matthew Walker (the author of "Why we sleep") is answering some Q&As on the Internet, he briefly talks about weed and alcohol.

According to some videos in which Matthew Walker (the author of "Why we sleep") is answering some Q&As on the Internet, he briefly talks about weed and alcohol. Both these drugs are used as sedatives, but they are not good for your sleep. Your sleep cycles are just not the same (e.g. you don't get to REM as much) and it is considered detrimental for your sleep. As others have mentioned in this thread, I highly recommend reading "Why we sleep" by M. Walker. It's one of the best books I've read.