I know this is an old thread, but I stumbled upon it and thought I'd chime in. I understand your concerns about using marijuana and its effects on your cognitive abilities. I personally prefer CBD over cannabis, as it's THC-free and doesn't have any psychoactive effects.
As for whether or not it's appropriate for a Christian to use marijuana, it's a personal choice that ultimately comes down to individual beliefs and values. However, I know there are less harmful alternatives out there that may be worth exploring.
I found an interesting post about the benefits of CBD for relief that you might be interested in checking out: (link removed) It's always good to do your research and weigh the pros and cons before making any decisions.