My illnesses were not psychosomatic..but Vick's Vapo rub might just be a Placebo ...that works.
When I was a kid, sometimes the whole house smelled like: "Vick's Vapo Rub." There might be three or four of us down with varying respiratory infections. Some had to use the "Vaporizer" with Vicks Vapo Rub being turned into well, a vapor. LOL
Most times tho...my Mom, or an older sister just rubbed a whole bunch of it on your chest. It felt good. And most times it opened up your tiny little nose too.

I am not sure if it was the gentle rubbing of my Mom's hands, or my sisters. But if you were five...and sick...it helped- a lot! Maybe it is that unique smell, or how it warmed your skin, but seventy years later, I can still feel its effects.
So last month, I bought a small blue bottle of it. And yep, every night before I go to bed, I dab a bit under my nose. I don't rub it all over my chest, because I hate feeling greasy in my old age.
And I guess it does have a psychological effect, because I go back to being a kid, warm, snuggled up, cared for...and then I drift off to sleep.
Sometimes at School, up until about Sixth grade, the whole Class might smell like Vicks Vapo Rub. And the Nuns all kept one of those blue bottles in their desk. And they too, would rub it gently on your neck and chest, with a little dab under your nose. And you would make it through the School Day.
Powerful stuff that Vick's VapoRub. In my case it has lasted seventy four years and counting.