Stress affects people differently.  Some people experience mainly behavioral, emotional, or somatic symptoms.  While others may experience a combination of symptoms. The human stress response is caused by both internal and external stressors.  A person may become stressed because of all the demands from school, home, children, work, etc. These are external stressors.  But, people also become stressed by rumination.  Rumination is the preoccupation with our own thoughts.  Humans can become preoccupied with thoughts that turn on the human stress response, which is a major consideration in depression and other psychiatric symptoms.