The type A personality is characterized as being very time conscious, highly competitive, rather inflexible and sees change as stressful.  This personality type is often judgemental of others and is considered highly critical. In addition, this personality type exhibits anger and hostility when dealing with conflict. 

Roseman wanted to see if there were any health effects correlated with this personality type.

The study was a prospective study of 3,154 employed men aged 39 to 59 years. The study was quasi-experimental design, looking at the incidence of coronary heart disease over a period of 8.5 years. During that period 257 of the participants developed coronary heart disease. The researchers found a significant link between heart disease and cholesterol levels, cigarette smoking and systolic blood pressure. But they also found a link to personality.

70% of the men who developed coronary heart disease had Type A personalities.  When participants were matched for smoking, exercise, cholesterol levels and systolic blood pressure, type A were nearly twice as likely to develop heart disease as Type B people.

There is some question as to why Type A personalities may have higher levels of cardiovascular disease. Irribarren et al (2000) argues that it may the result of poor health habits, high risk behaviours and/or physiological mechanisms. For example, type A personalities have been found to have high cardiovascular reactivity - that is, a higher blood pressure and heart rate response to stress.  They have also been found to have a prolonged HPA axis response to stress or exhibit other symptoms of chronic stress.

A strength of the original study is that it controlled for other important variables, such as smoking and lifestyle. This helps us to rule out those variables as the primary cause of the problem, rather than the personality type. However, coping styles for stress were not studied in the original study.  This may have played a key role in the development of heart disease.

Limitations of the study involve problems with external validity.  Because the study used an all male sample it was unknown if the results could be generalized to a female population. Studies carried out on women have not shown such a major difference between Type A and Type B and subsequent health. This may suggest that different coping strategies are just as important as personality.

The research is also based on the assumption that the constructs of "Type A" and "Type B" personality are valid.  This may not the case.  Personality theory actually argues that people are much more complex than these two labels imply.