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What Is a Medical Nexus?

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A medical nexus (clinical-to-legal bridge) is the evidence-based connection between a veteran's current diagnosed condition and military service. In the context of a VA disability claim, a nexus addresses whether the veteran's psychiatric or medical condition is at least as likely as not (a 50% probability or greater) related to an in-service event, injury, illness, exposure, or other service-related factor.

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Medical Nexus = Evidence-Based Connection

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A medical nexus may be established through one or more of the following:

• Direct Service Connection: The condition was caused by an in-service event, injury, illness, or exposure.

• Incurrence During Service: The condition first developed or manifested during active military service.

• Aggravation: Military service permanently worsened a pre-existing condition beyond its natural progression.

• Secondary Service Connection: A current condition developed as a result of an already service-connected disability.​

 

For example, Post-Traumatic Stress Disorder (PTSD) may be directly related to traumatic experiences that occurred during military service. However, service connection is not limited to conditions with a direct causal relationship. A psychiatric or medical condition may also qualify if it first manifested during active military service or if military service permanently aggravated a pre-existing condition beyond its natural progression.

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An independent medical nexus opinion may be particularly valuable when the relationship between military service and the veteran's current condition is not readily apparent, when the available medical evidence is conflicting or incomplete, or when additional clinical clarification is necessary.

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A comprehensive nexus evaluation includes a thorough review of military and medical records, applicable diagnostic criteria, relevant scientific literature when appropriate, and an objective medical analysis. The resulting opinion addresses whether it is at least as likely as not that the veteran's diagnosed condition was caused by, incurred during, aggravated by, or secondarily related to military service.

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