AN EPIDERMIOLOGICAL APPROACH TO AETIOLOGY
In epidemiological, one of the aims is to assess the independent association between a potential risk or prognostic factor. It is, however, extremely important to keep in mind that in most disease and injuries, a multifactorial casual model is needed to understand the onset and prognosis.
This can be effectively discussed using the ‘pie’ model, or the component cause model, introduced to epidemiologists by Rothman. Some prognostic factors that may be involved in recovery from WAD are introduced in two different ‘pie’ models.
According to the ‘pie’ model, all contributing causes in one of the sufficient causes, or ‘pie’ are needed, in order to recover from WAD. Each sufficient cause represents one of presumably several alternative routes leading to recovery. The interactions between contributing causes are illustrated as separate ‘pie slices’ included in the same pie. Slices in one ‘pie’ are said to interact, because it is their joint action that leads to recovery. In real life, of course, different distributions of biological, psychological and social factors occur among different people.
In the literature, there is no recognized necessary for recovery from WAD. Neither has any sufficient cause been identified. Instead, several contributing causes (i.e. factors that affect the cause of recovery) have been found. When linking this ‘pie’ model to the evidence of prognostic factors in WAD, numerous sets of possible ‘individual pies’ become obvious. In summary, several different sufficient causes for recovery from WAD exist; in other words, several alternative routes lead to recovery.
In research, the effect of individuals contributing causes, or risk factors, are usually investigated for the condition in question. Complete sufficient causes usually do not lend themselves to studies because few of these scenarios actually exist (exceptions include bacterial infection). Still, it is important to keep the ‘pie’ model in mind when interpreting and discussing empirical results on risk and prognosis. A single contributing cause may otherwise be confused for a sufficient cause. The whole picture for specific sets of sufficient cause is seldom discussed in the research of WAD or in other contexts.
The casual process is more complicated than explained by the ‘pie’ model, since effects are more likely to depend on other factors that happen simultaneously. For instance, some persons in pain may call for support from family members or workmates, which in turn may change the person’s future pain perception and behavior (positively or negatively). In other instances, pain intensity may cause depressed mood, or depressed mood may cause more pain (bidirectional). Nevertheless, this component cause model is a fruitful way to conceptualize WAD as it visualizes the multifactorial nature of WAD and how biological, psychological and social factors may interact.