Secondary Service Connection: Conditions Caused by Your Disability

Most veterans think of a claim as one condition tied to one event in service. Secondary service connection is different. It covers a condition that your already service-connected disability caused or made worse. The rule lives in 38 CFR 3.310, and it opens a lane a lot of veterans never use, because they do not know it exists.

The 3.310 language quoted below was verified against the eCFR and VA’s guidance on July 9, 2026.

What the regulation actually says

Section 3.310(a) is short and broad: a “disability which is proximately due to or the result of a service-connected disease or injury shall be service connected.” Proximately due to means your service-connected condition is a real cause of the new one, not just something that happened around the same time.

There are two ways to win a secondary claim:

• Causation. Your service-connected disability caused a new, separate condition.
• Aggravation. A condition you were not service connected for got permanently worse because of a service-connected disability. Section 3.310(b) allows this, but it sets a bar: VA “will not concede” aggravation unless the baseline level of severity of the non-service-connected condition is established by medical evidence from before the aggravation began. VA then rates only the amount of worsening above that baseline, subtracting out any change that is just the natural progress of the disease.

The nexus is what claims turn on

A secondary claim needs three things in the file:

1. A current diagnosis of the secondary condition.
2. A disability that is already service connected.
3. A medical nexus opinion linking the two, with reasoning.

That third piece is where most secondary claims are won or lost. The examiner or your private physician has to explain, in medical terms, why the service-connected condition is at least as likely as not the cause (or the aggravator) of the new one. A bare assertion that two conditions are related is not a nexus. The reasoning is the evidence. See what a C&P exam measures for how VA documents that link.

Common real pairs, framed honestly

These pairings come up constantly, and each still needs its own nexus evidence. None of them is automatic.

• Sleep apnea secondary to PTSD. Research links the two, and it is a frequently granted secondary, but you still need a physician to connect your sleep apnea to your service-connected PTSD or mental health condition rather than to age or weight alone.
• Peripheral neuropathy secondary to type 2 diabetes. When diabetes is service connected, the nerve damage it causes in the feet and hands is a classic secondary. The claim turns on a diagnosis of the neuropathy plus a clinical link to the diabetes.
• Depression secondary to chronic pain. A service-connected orthopedic or nerve condition, such as a rated back disability driving radiculopathy, can produce a diagnosable depressive disorder. The nexus has to tie the mental health condition to living with the pain.
• Erectile dysfunction secondary to PTSD medication. ED is often caused not by the mental health condition itself but by the SSRIs prescribed to treat it. That medication side effect is a recognized secondary path, and it can also open special monthly compensation for loss of use.

The honest read: every one of these is winnable, and every one of these is deniable without a clear medical opinion. The pattern being common does not lower your evidence burden.

If any of this involves mental health, you do not have to wait on a claim to get help. The Veterans Crisis Line is 988, then press 1 (or text 838255), available 24/7.

How to file

A secondary claim is filed on the same VA Form 21-526EZ as any disability compensation claim. Name the secondary condition and identify the service-connected disability you are linking it to, so the rater knows you are claiming it as secondary and not as a fresh direct claim. If you need time to gather a nexus letter, file an intent to file first (VA Form 21-0966) to hold your effective date for up to a year.

What it does to your rating

A granted secondary condition is rated on its own and then combined with your existing ratings, which never means simple addition. Run the real math on the combined-rating calculator and check the pay tables to see what the new combined figure pays. If VA denies the secondary link or lowballs the aggravation, that is exactly the kind of decision the decision-review process exists for.

You can build a secondary claim yourself, but a VA-accredited representative or VSO will help you frame the theory and line up the nexus evidence, and their claim help is free.