Define causal complements in the component-cause model.

• A. The primary necessary cause.
• B. A single factor that always guarantees disease.
• C. The combination of all possible factors.
• D. Additional components beyond the selected one that form sufficient causes.

Answer: (D)

In the component-cause model, a disease occurs when one sufficient cause pie is completed by its component causes. A causal complement of a given component is the other factors that, together with that component, form a complete, sufficient cause. This means that that single component on its own does not guarantee disease; it requires the presence of the complementary components to produce the outcome. For example, a genetic susceptibility component may be part of a pie that also requires certain environmental exposures to cause disease. The same component can have different complements in different pies. The other ideas don’t fit: a single factor that always guarantees disease isn’t realistic in multifactorial diseases; a primary necessary cause would imply universality across pies; and the combination of all possible factors isn’t the mechanism, since only specific subsets form sufficient causes.