Typically it is said when listening to someone talking-- it is a polite way to let them know that you are paying attention. Think of it as going 'mm' or 'ah'.
There are numerous emotional and physical disorders that have been linked to stress including depression, anxiety, heart attacks, stroke, hypertension, immune system disturbances that increase susceptibility to infections, a host of viral linked disorders ranging from the common cold and herpes to AIDS and certain cancers, as well as autoimmune ...
Unresolved anger issues lead to anxiety, which can have long-term effects on your life. Immediate effects of anxiety might include dizziness, rapid breathing, nausea, muscle pain, muscle tension, headaches, and problems with concentration and memory.