"Decreased immunity" refers to a condition where the body's ability to fight off diseases and infections becomes weaker or less effective than normal. Full definition
When this response is chronically activated, people can suffer from decreased immunity and other health problems. (goodtherapy.org)
Beyond that the adrenal gland responsible for secreting the stress response hormone becomes fatigued, resulting in decreased immunity to infection, reduced ability to repair the body and increased inflammation and tissue damage. (canadianbusiness.com)
Stress also decreases immunity and disrupts your sleep. (8fit.com)