Type D personality traits can be harmful to your health and relationships. Do you tend to feel gloomy, keep to yourself, hide your emotions from others and tend to see the glass as half empty? You might be a type D personality. Personality types were originally identified by cardiologists in the 1950's to help determine patients who might be at greater risk for heart disease. As research has continued to develop over the years, more personality types have been identified and labeled with specific letters to represent a found set of patterned personality traits. You have likely heard of type A personality before, which involves traits such as competitiveness, aggressiveness, and high levels of ambition. People with type A personality are found to be at greater risk of experiencing cardiac health complications such as high blood pressure and heart disease. When we discuss personality types like this we are not referring to an established mental health diagnosis, bu...