Here's an interesting blog I found, written by Lynn Drake MD, that breaks down the affects that stress can have on your hair.  Below is a short excerpt of the article...

When the body and our heath is negatively affected (trauma, pregnancy, emotional stress, major illness) your hair no longer has priority for your health maintenance.  It's as if your body is saying, "I've got bigger problems to worry about and take care of, I don't need to worry about hair growth right now." 

Your body's built-in self healing "process" considers your other problems so important, that it concentrates on those problem and ignores your hair.  Severe mental stress can have this affect as your body and mind tries to deal with your emotional issues. This process, known as telogen effluvium, occurs when more hairs go into a "resting phase" and are shed.  Telogen Effluvium is characterized by sudden, diffuse hair loss caused by an interruption in the normal hair growth cycle. This interruption is often the result of trauma, such as chemotherapy, childbirth, major surgery, severe stress, and severe chronic illness. This trauma causes large numbers of hair follicles to enter a stage of telogen, or rest, simultaneously.

The telogen phase can last 6 to 12 weeks (and much longer if left untreated) and affects women much more then men.

To read the full article please click here.

Source: HairLossLibrary.com