Yes I do, although not in the way you suggest - if I drank decaf coffee, I would not expect caffeination effects. A little ambiguity goes a long way, and I am willing to take eyes-wide-open advantage of that:
There have been health-related circumstances in my life where there might be a palliative or an explanation, but there is no evidence-based conclusion, and I have chosen to believe that steps I’ve taken have helped.
Case in point: Years ago I started having weird intestinal cramps (probably stress-triggered, as they began during a really stressful time in my life). I got diagnosed with IBS (Irritable Bowel Syndrome) which it seems to me is basically “yeah, your bowels hurt … we don’t know why but nothing seems to be super wrong, so get on with your life.”
I did get on with my life. Then several years later, the symptoms miraculously disappeared for several (still stressful) years. And then they came back.
So what changed? The water I drank. When I was on city water, which is chorinated, I had IBS. When I drank non-city water, the symptoms disappeared.
So I have been IBS-symptom free for a while, until recently, when I changed my drinking water source back to city water, and the symptoms came back.
Now I have gone back to the other water source and the symptoms are going away.
To be clear, there is zero science, merely speculation, behind these changes. Maybe the water has nothing to do with my symptoms. No where have I found any evidence-based information to support my experience.
So I’m basically relying on the placebo effect, and I am well aware of this. What I say is:
“It might be all in my head. But my head is where I live.”