With respect to hair loss, stress causes the scalp to tighten, making the hair thinner and more inclined to hair loss. Also, tightening neck muscles and arthritis restrict blood flow to the head. This can be countered through neck massage.
Stress may well be considered a primary aggravator to many, many diseases and chronic health conditions such as heart disease, weak immune systems and cancer.
A JAMA article examined the evidence that stress influences major diseases.
" ... In the JAMA article, the authors consider the behavioral and biological mechanisms through which stress contributes to disease and weigh the results of studies that have examined whether stress plays a role in depression, cardiovascular disease, HIV/AIDS and cancer. Those studies reveal that stress plays a role in triggering or worsening depression and cardiovascular disease and in speeding the progression of HIV/AIDS."
Source: Science Daily