There are many different causes of stress. Stress can be physical (overexertion, poor postures, changes in season, lack of sleep, accidents), emotional/mental (exams, fights with partners/bosses/children, loss of a loved one, work/financial problems), or even chemical (low water intake, processed foods, polluted air, smoking, hormonal imbalance). Each of these stresses can affect the body in many different ways eventually leading to chronic problems..
Long term effects of stress:
Intestinal, immunological and reproductive problems
Overall decreased health and quality of life