By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – Our mood can affect our health – and you might be surprised how it happens.

For instance, when you’re depressed, your body produces more inflammatory proteins called cytokines. They can make pain worse and also increase your risk for heart disease, strokes, heart failure, and heart attack.

In addition, studies have shown that hormonal shifts, inflammation, and mixed signals sent from the brain to the heart might explain the links.

Depression is not the only issue. Loneliness increases your risk of heart disease and of death from heart problems.

As much as negative feelings can hurt, positive feelings can help. Optimism, happiness, and satisfaction with life have been shown to lead to improved cardiovascular health.

People who believe their life has meaning and purpose tend to live longer than their counterparts. In part, this may be because positive people take better care of themselves.