Warning: The following statements are partial speculation. Make of them what you will and hopefully they will help you generate an adequate answer.
-Individuals with clinical depression are less likely to go out, as they feel less inclined to socialize and are likely to lose the drive to leave their homes and perform daily tasks. Your body needs exercise and neglecting to use it can't be good.
-People who are depressed are more likely to develope eating disorders such as anorexia and binge eating. Both place strain on the heart and body in multiple ways.
- If you understand how a Placebo works, you know that how how a person feels physically can be linked to mentality. If an individual thinks they are being given a life saving medicine when they are only receiving a sugar tablet, their health may still inprove slightly. By this logic, we can assume an individual with a declining mental health has a chance to show a decline in physical health.