Thank you for your messages everyone. I know that there can be triggers, without a doubt, but for me it is pretty rare. In the last fortnight I had a few very stressful events occur and yet it was the longest I've been baseline for months. I had regular emotions regarding the situations (like anger and fear) but my mood continued on its usual pattern, unaffected. When I told one of my doctors that I had been quite stable the last few weeks she asked (again) what happened to cause that? Ahhhh!