New research indicates that those who lead a happier lifestyle also appear to be healthier. In a recent study of nearly 3,000 adults, British researchers found those who reported being happier had lower levels of the hormone cortisol, also known as the "stress" hormone. Since higher levels of cortisol increase blood pressure, lower immune function and can even increase adominal fat deposits, keeping cortisol levels low is optimal for ones health. Thus, those under psychological stress at work and at home will experience elevated cortisol levels which in turn can adversely affect their cardiovascular and immune health as well as contribute to obesity. Aside from exercising and eating right, it also appears leading an overall "happy" lifestyle is important for maintaining one's health.
Source: American Journal of Epidemiology, January 1, 2008.