How is GDP affected by the sale of an hour session with a psychical trainer?

Question

How is GDP affected by the sale of an hour session with a psychical trainer?

Answer 1

It's a service that is consumed, so it is part of consumption.  An increase in consumption increases GDP.

Then the physical trainer (or psychiatrist, if that's what you mean) pays taxes and either spends or consumes this extra income.  The consumption directly affects GDP in the same way as above, and the cycle continues.  An increase in savings decreases the interest rate, which increases investment, and since investment is a component of GDP, GDP increases from the investment as well.  But since the amount involved is so small, the effect is quite small.