Friedman and Rosenman aimed to determine if there was a link between stress-related illness and personality type. They studied over 3,000 men and found that those with a Type A personality (ambitious, restless, pressured) were twice as likely to have died from cardiovascular problems than those with a Type B personality (relaxed, slow-speaking). They concluded aspects of personality are linked to coronary heart disease and that stress may be the key factor.