She usually notices pretty fast. I think, in the beginning of our time together, I poured out most of my life story in the first of 3 weekly meetings, and then asked her if she had a diagnosis.
These days, she can usually tell that I'm sliding or have slid, into The Pit, from my tone of voice, the way I sit on the couch, how I look (tired, for instance), what I say, etc. Sometimes I say I am only tired, or that I didn't sleep well, but, as we get deeper into the session, I tend to agree with her.