Scorpiosis, there are many different types of groups, and you can find a lot of variation in duration. I think it is common for a "closed" group to run 6-12 weeks. But there are some groups that are ongoing. New members are added, old members leave, and the group endures throughout this turnover. I did a support group for new moms with their babies, and it lasted 10 weeks. I did Weight Watchers--another type of support group--and it was ongoing. Right now I am doing a group as part of a course I am taking, and it is 8 weeks long. My daughter's therapist has a group of women who have been together several years.

Before you join a group, you can ask about the screening process and tell your worries about being in a group that is too heterogeneous with regard to behavioral health. I do not think the group leader will think ill of you for this. Somewhere out there is a group that will work for you. It just may take a little time to find it.