The stereotype is that marijuana makes you stupid. This certainly seems to happen in the short run. A 2016 study led by Staci Gruber, Ph.D. suggests that medical marijuana may actually improve executive functioning in adults.
If you are making your own CBD oil you can tailor your blends of terpenes to include terpenes that are activating for morning use and terpenes that are sedating for evening use.
The January 5, 2019 issue of the Wall Street Journal included a piece by Alex Berenson entitled “Marijuana Is More Dangerous Than You Think.” It is based on an upcoming book Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence. Berenson argues that legalization of marijuana has resulted in increased violence and mental health problems.