I dont know about guiding but I do about scouts I was a leader, I have never been sectioned however I have been a phych hospital as a voluntary paitent.
A disclosure check is done and if it showed up on mine no one commented on it so I assume it wasnt.
I found it hard going as I drift off and when in charge of children that is not a good thing....
I am a CSL of a cub pack. I have never had any problems in terms of MH, however its not something I have been all that open about with the other leaders either. The only issue I have found is the factor of spending too much time doing scouting things and not having time for myself. I did find running the pack rather overwhelming this term and as a result have not attended every week. The likehood for me personally is that I will not return back at the start of the term, I will take a break until I feel a little more motivated.
I also used to run climbing at a scout activity centre too, but it all became too much and I have just stopped going to that.
Good luck with your scouting and guiding sections.