"In small studies, smoking cannabis (marijuana — the dried parts of the cannabis plant) has improved IBD symptoms, including pain, nausea, and decreased appetite.

However, there is currently no evidence that medical cannabis can reduce IBD inflammation or improve disease activity. Further research is needed, and underway now, regarding the impact of cannabis on IBD." 

References:

1. https://www.crohnscolitisfoundation.org/complementary-medicine/medical-cannabis