Cohen's study used a true experiment where the independent variable was manipulated, whereas Kiecolt-Glaser's study was a natural experiment. So, the question is - which is more important?  Internal validity - which Cohen has a higher level of - or external validity - which Kiecolt-Glaser has a higher level of.  Either answer is correct, as long as it is justified.

Unlike biological models, Lazarus & Folkman's model helps to explain individual differences in stress reactions and the long-term health of individuals, regardless of how many stressful life events an individual may experience.

First, we should be concerned that the research is so recent. In order for us to draw a strong conclusion about the results, the study needs to be replicated. Because the study was both longitudinal and prospective in nature, this will be difficult to replicate. Secondly, the variable of "optimistic" vs "pessimistic" was measured through self-reported data. This could be problematic and affect the validity of the study. Lastly, since the study took place over six years, you should wonder how many times the cortisol levels of the participants were measured; it was only 12 times. The study does, however, raise some interesting questions and generates further research. Time will tell if the conclusions can be supported.

In a cross-sectional study, participants of different ages are compared at the same time.  This gives us a snap-shot of their health but does not give us an indication of change over time, which is what we see in longitudinal research.

This means that the higher the "dose" of adverse childhood experiences, the higher the level of health problems. So, the more frequent and intense the ACEs, the more likely a child will develop health problems.

The sample size is large, so we should be able to generalize the findings to other British workplaces that work in a similar hierarchical structure.  It may also be possible to generalize the findings to other European workplaces.  However, the British Civil Service may not be equivalent to an American private company structure. In addition, cultural dimensions (for example, power distance) are not considered in the study. This may also limit the ability to generalize the findings to other populations.

Tung & Gilead were actually able to manipulate the IV - that is, the monkey's place in the social hierarchy. Sapolsky carried out a naturalistic observation and did not interfere with the natural hierarchy.  This may mean that there were individual factors that may have determined the baboons' place in the hierarchy which may have influenced the outcomes of the study.

Operario argues that it is one's subjective feeling about poverty that leads to the stress that leads to poor health. That means that it is not one or the other - but the interaction of sociocultural - that is, the environment in which the individual lives - and cognitive - their perception of their situation compared to others. Specifically, he looked at the role of upward comparison - that is, comparing yourself to people who have more than you do.  Those who engage in downward comparison - comparing yourself to those who have less than you do - tend not to experience the same level of stress.