[wasabi991011]

This doesn't sound right to me.

I've heard people speculate about the opposite actually: psychological stress causing the an overactive immune system, resulting in chronic inflammation and a prevalence of auto-immune disease.

I'm a layman though, would like for someone to clarify.

[tsoukase]

You probably refer to the psycho-immunology, a different aspect. I refer to onco-immunology which is even less explored. In the past many proposed a connection between stress and cancer but without evidence and ground. I think it's time to approach it with enough scientific rigor.