Cbn = cannabinol. It's a byproduct of thc breaking down with age, but it naturally present in small amounts anyway. It's the cannabinoid some people find really useful for sleep. If you have some REALLY OLD weed, especially not sealed in an airtight container, you might find that it makes you sleepy.
CBD itself is not going to make someone sleepy, but could help with a racing mind. I try to avoid thc during the week. It messes with rem sleep. I find that if I have thc during the weeknight, there's a subtle change in my mental clarity the next day? Is it as bad as alcohol? Nope. But I can tell.