Doctor Dissects the Wim Hof Method - Cold Hard Science Analysis

How hyper-ventilation reduces the sensation of pain and that the placebo-effect affects the immune-system;

Source: https://www.youtube.com/watch?v=D6EPuUdIC1E

Quotes

A rise in pH to around the levels achieved by hyper-ventilation can actually de-active them [the ASIC3], effectively improving the pain-threshold.

– at 20m31s

That's exactly what the placebo effect is: Mild changes in immune-system response can be observed purely based on a person's belief about what the outcome will be.

– at 22m21s