IBD and mental illness are definitely tied together. The mental illness affects the digestive tract greatly. If you are not happy or suffering from mental illness, it can definitely have a huge impact on the digestive system. Here are some cool articles:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4073018/
https://www.health.harvard.edu...gut-brain-connection
https://www.crohnscolitisfound...h/depression-anxiety
https://www.webmd.com/ibd-croh...ession-crohns-linked
Let me know if you would like more