The Western Collaborative Group Study

Beginning in the late 1950s the cardiologists Meyer Friedman and Ray Rosenman launched the Western Collaborative Group Study, a large longitudinal investigation following more than three thousand healthy middle-aged men over roughly eight and a half years to test their hypothesis that a personality pattern they termed Type A behavior, marked by intense competitiveness, impatience, hostility and a chronic sense of time pressure, predicted the later development of coronary heart disease. Participants were classified near the start of the study as exhibiting the Type A pattern or the more relaxed, less urgent Type B pattern, based on a structured interview and questionnaire Friedman and Rosenman had developed, and were then tracked for the subsequent development of heart disease. The study's early results, reported through the 1960s and 1970s, found that men classified as Type A developed coronary heart disease at roughly twice the rate of men classified as Type B, even after accounting for established risk factors such as smoking, blood pressure and cholesterol, and the Type A and Type B typology entered both scientific and popular usage as an explanation for who was and was not at risk of heart disease. Later research substantially narrowed this conclusion, finding that the specific component of hostility, rather than the broader Type A pattern as a whole, carried most of the study's original predictive power, and subsequent studies have not consistently replicated Type A behavior as an independent overall predictor of heart disease. The Western Collaborative Group Study nonetheless remains a foundational reference point in health psychology's study of the relationship between personality, chronic stress and physical illness.