Under 38 CFR § 3.310, a disability that is caused or aggravated by an already service-connected condition is itself service-connected. This is one of the most under-used pathways in the entire system — because the VA almost never volunteers the connection.
Common secondary chains
- Sleep apnea secondary to PTSD or the medications used to treat it
- Radiculopathy secondary to a service-connected back injury
- Depression secondary to chronic pain
- Diabetic peripheral neuropathy secondary to diabetes
- Hypertension secondary to PTSD
What proves it
Secondary claims live or die on the medical nexus opinion. The opinion must connect the secondary condition to the primary service-connected one, using the “at least as likely as not” standard and a clear rationale. Aggravation counts too — if service-connected condition made a non-service condition worse, you are owed for the worsening.