How are stress and trauma related to depression?

Can be causes of it.: Depression can be a direct result of any type of stress including trauma - physical, emotional, sexual trauma to name some. Stress is personal. What stresses one person may not stress another. Stress isn't always something bad - getting married, having children, changing jobs, moving - can be stressful. What happens under stress (including trauma) can cause depression & may need professional help.

Physical, Emotional: Severe traumatic events are known to cause a variety of chemcial changes in the brain that can be linked to emotional problems such as depression. In addition, and probably connected to the chemical changes, it is well known that trauma can negatively affect a person's outlook concerning the world and his/her future. This can also lead to depressive symptoms.