Differnt ways. People with mental health issues tend to neglect their physical health. In addition conditions like anxiety and depression can cause deterioration of physical health. All illnesses are both physical and mental. Every month professional journals are indicating how this occurs. Some of the processes are simple and some are very complex.
Good Question. It is a well established fact the chronic mental health issues lead to an increased risk of a variety of physical problems. The causes are probably multi-factored. Mental illness tends to lead to a sedentary lifestyle. Also, there are probably many hormonal and neurochemical interactions that lead to problems both emotionally and physically.