Differentiate between association and causation using the causal guidelines. Discuss which
of the guidelines you think is the most difficult to establish. Discuss the four types of causal
relationships and use an example not listed in the textbook to describe each relationship.

Causation and Association
In epidemiology, the main objective entails the assessment of the primary causes of
disease. Nonetheless, since most studies in this field are observational by nature, several
explanations provided for an observed association should be put into consideration before
inferring that a cause-effect relationship exists. On the one hand, association refers to the
correlation between two variables, exposure and an outcome which occurs as a result of the
effects of chance (random error), bias (systematic error), and reverse causality (Broadbent,
2016). These may be coupled with confounding factors and true causality. On the other hand,
causation describes the changes in one variable that occur as a result of alterations in the other.
However, these two aspects differ by the fact that in the association, some measures cannot be
directly administered or applied to determine the changes in the subjects as it would be unethical.
Among the various causal guidelines, the most difficult one to establish entails the
experimentation phase that involves the removal of the exposure, which ultimately alters the
frequency of the outcome. Besides, the four types of causal relationships include the necessary

but sufficient correlation that describes the occurrence of disease only in the presence of the
causative factor and exposure to it leads to the affirmation of the first premise (Broadbent, 2016).
For instance, during a disease outbreak, thousands of people may be exposed, but only a few
individuals do not develop the related disease due to other variables such as low infectivity rate
and their immunity status among others. The second type of causal relationships is described as
necessary but not sufficient. In this case, more than one factor is required in a temporal sequence
for the occurrence of a disease (Broadbent, 2016). For instance, the crucial factor for the
existence of lung cancer is cigarette smoking. However, its presence may not be sufficient to
produce the condition on all individuals.
Thirdly, the sufficient but not necessary relationship describes specific factors that lead to
the development of an illness, but other elements (risk factors) may be associated with the
occurrence of the same disease. For instance, obesity can be classified as a risk factor for
diabetes, but other factors may lead to the development of the illness. The fourth type of
causality relationships includes neither a sufficient nor necessary category that occurs as a result
of the combination of specific factors to produce a particular disease (Broadbent, 2016).
Nevertheless, the condition may occur in the absence of various factors. For instance, cardiac
diseases are brought about by numerous risk factors.



Broadbent, A. (2016). Causation in Epidemiology and Law. Forensic Epidemiology, 111-130.