Some people take up negative coping methods such as consuming too much caffeine. People with high stress often use it to jump start there energy, and make them more productive, which can lead to a caffeine addiction. Others smoke, or drink in excess which again turns into a drug habit into addiction. Some people compulsively spend money thinking material things will relieve their stress. Finally, one of the most common negative responses to stress would be emotional eating, which can lead to obesity and other health problems.
Hope that helped.