Not a lot is known about CBN yet. It is thought that it is just degraded THC, however there are strains that are naturally high in it. I have a perfect example...
Moonshine Haze cup cut. It is a fast sativa, very amnesia haze dominant. Usually sativas are daytime smoke. However for me I get extra high from this herb for some reason. So I never smoke it as daytime weed. It made me curious as to why this sativa got me so high that I couldn't really get my shit done the way I can on a normal sativa. So I had it Lab tested. THC 16.31%, CBD .48%, but the kicker is CBN 1.09%. This is on a 70 day sativa, with mostly clear and cloudy trichs, no amber at all, cured for two weeks. When these numbers came back the lab tech commented on how unusual such high CBN is when there are no amber trichomes at all. CBN seems to be responsible for that fuzzy, tunnel vision, flicks of light type of high. I showed my results to DJ short and had about a half hour discussion with him about CBN, where we looked at all of his lab results trying to find strains naturally high in CBN, and to see what his levels were on his herb cured for years... The CBN on my moonshine was higher than 90% of his tests until it got to the herb cured for 2+ years.