Now that I have Crohn's and am on various meds, I can't really sort out the chicken from the egg anymore. But in the past, when I was 100% physically healthy, I can definitely say that the depression preceded the fatigue. It was unreal how tired an otherwise healthy teenager could get - I felt like I was weighted down with heavy weights and the smallest task would take a mammoth effort. When the depression lifted I would return to my normal energy levels.
Physical stuff, like major operations and chronic pain, will also heavily take it out of you. I can testify to that as well!
Hope this helps a bit :-/
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)