Other 7 Ways People Used Cannabis In The 1930s

My close friend has suffered two concussions within a gap of 2 months: once after falling during skiing, and once in a road accident. That was about 1 year ago and he still suffers from the post-concussion condition, which is hardly endurable. Moreover, he feels hypersensitivity to sound and light, tiredness, some dizziness, some cognition impairment.

He is uncertain to try something that might further harm his cognitive function but he is willing to give cannabis a try (now that it is legal in many states).

I just want to know, is there any fruitful research on the effects of cannabis on a concussed brain?

Thanks
Mary