Which component is essential for establishing a causal relationship in secondary service connections?

The essential component for establishing a causal relationship in secondary service connections is demonstrating a proximate cause between conditions. This means that for a secondary condition to be recognized as connected to a primary service-connected condition, there must be clear evidence that the primary condition has directly led to the development or worsening of the secondary condition.

This concept is crucial because it ensures that the relationship between the two conditions is not just coincidental but is instead a direct result of the primary service-connected condition affecting the individual’s health. Proximate cause comprises medical opinions, clinical evidence, or scientific research that indicates how one condition can lead to or exacerbate another condition, fulfilling the requirement for a secondary connection.

In contrast, other components such as evidence of aggravation during service, a diagnosis of the primary condition, or medical treatment received during service play roles in different aspects of establishing service connection but do not directly address the causal relationship necessary for a secondary service connection. These components may support a claim but alone do not suffice to illustrate that one condition is a result of another without the crucial link established by proximate cause.