Claim Raven explanation
What this means
This is the rule for secondary service connection. It addresses a disability caused by a service-connected condition and an increase in severity caused by that condition rather than natural progress.
Secondary service connection involves the effect of a condition VA has already recognized as service connected on another disability. Causing another disability and worsening an existing one are different questions. The records and any medical opinion should explain the relationship that is actually supported, including the rule's additional requirements when aggravation is involved.
How this helps your claim
This rule helps you recognize the two questions in a secondary service-connection review: did an already service-connected disability cause another condition, or did it worsen that condition? Those are different questions. It can help you spot an opinion that discusses only causation when aggravation is also raised by the evidence.
What to check in your records
If a relationship is relevant to your history, look for medical evidence explaining it and the records the clinician used. Distinguish causation from aggravation.
- Confirm which disability VA has already recognized as service connected and which other condition the records identify.
- Read medical opinions for a clear explanation of causation, aggravation, or both, including the history and findings used.
- For aggravation, look for medical records showing severity before the worsening, the earliest available evidence around that change, and current severity. The rule below explains its baseline requirements.
Ask which relationship the opinion actually addresses
An opinion may explain why one condition did not cause another without addressing whether it worsened the other condition. Read its conclusion and reasoning carefully. The words caused and aggravated identify different questions, and a conclusion about one should not silently be treated as an answer to both.
For a worsening question, arrange the relevant medical history before and after the reported change. Describe the documented course and the records used by the clinician. Do not invent a baseline, assume every fluctuation is aggravation, or treat a possible association in a study as proof of an individual relationship.
Does having two diagnoses establish secondary service connection?
No. Coexistence is different from a supported causal or aggravating relationship. The evidence needs to address the relationship actually at issue under the applicable rule. A clear medical explanation can be more informative than repeating that the conditions occurred at the same time.
Official regulatory text
38 CFR § 3.310
eCFR snapshot: September 3, 2026. Layout and spacing are adapted for reading. The full section and its tables are included below.
§ 3.310 Disabilities that are proximately due to, or aggravated by, service-connected disease or injury.
(a) General. Except as provided in § 3.300(c), disability which is proximately due to or the result of a service-connected disease or injury shall be service connected. When service connection is thus established for a secondary condition, the secondary condition shall be considered a part of the original condition.
(b) Aggravation of nonservice-connected disabilities. Any increase in severity of a nonservice-connected disease or injury that is proximately due to or the result of a service-connected disease or injury, and not due to the natural progress of the nonservice-connected disease, will be service connected. However, VA will not concede that a nonservice-connected disease or injury was aggravated by a service-connected disease or injury unless the baseline level of severity of the nonservice-connected disease or injury is established by medical evidence created before the onset of aggravation or by the earliest medical evidence created at any time between the onset of aggravation and the receipt of medical evidence establishing the current level of severity of the nonservice-connected disease or injury. The rating activity will determine the baseline and current levels of severity under the Schedule for Rating Disabilities (38 CFR part 4) and determine the extent of aggravation by deducting the baseline level of severity, as well as any increase in severity due to the natural progress of the disease, from the current level.
(Authority: 38 U.S.C. 1110 and 1131)
(c) Cardiovascular disease. Ischemic heart disease or other cardiovascular disease developing in a veteran who has a service-connected amputation of one lower extremity at or above the knee or service-connected amputations of both lower extremities at or above the ankles, shall be held to be the proximate result of the service-connected amputation or amputations.
(d) Traumatic brain injury.
(1) In a veteran who has a service-connected traumatic brain injury, the following shall be held to be the proximate result of the service-connected traumatic brain injury (TBI), in the absence of clear evidence to the contrary:
(i) Parkinsonism, including Parkinson's disease, following moderate or severe TBI;
(ii) Unprovoked seizures following moderate or severe TBI;
(iii) Dementias of the following types: presenile dementia of the Alzheimer type, frontotemporal dementia, and dementia with Lewy bodies, if manifest within 15 years following moderate or severe TBI;
(iv) Depression if manifest within 3 years of moderate or severe TBI, or within 12 months of mild TBI; or
(v) Diseases of hormone deficiency that result from hypothalamo-pituitary changes if manifest within 12 months of moderate or severe TBI.
(2) Neither the severity levels nor the time limits in paragraph (d)(1) of this section preclude a finding of service connection for conditions shown by evidence to be proximately due to service-connected TBI. If a claim does not meet the requirements of paragraph (d)(1) with respect to the time of manifestation or the severity of the TBI, or both, VA will develop and decide the claim under generally applicable principles of service connection without regard to paragraph (d)(1).
(3)
(i) For purposes of this section VA will use the following table for determining the severity of a TBI:
Scroll sideways to see the full table.
| Mild | Moderate | Severe |
|---|---|---|
| Normal structural imaging | Normal or abnormal structural imaging | Normal or abnormal structural imaging. |
| LOC = 0-30 min | LOC > 30 min and < 24 hours | LOC > 24 hrs. |
| AOC = a moment up to 24 hrs | AOC > 24 hours. Severity based on other criteria. | |
| PTA = 0-1 day | PTA > 1 and < 7 days | PTA > 7 days. |
| GCS = 13-15 | GCS = 9-12 | GCS = 3-8. |
Note:
The factors considered are:
Structural imaging of the brain.
LOC—Loss of consciousness.
AOC—Alteration of consciousness/mental state.
PTA—Post-traumatic amnesia.
GCS—Glasgow Coma Scale. (For purposes of injury stratification, the Glasgow Coma Scale is measured at or after 24 hours.)
(ii) The determination of the severity level under this paragraph is based on the TBI symptoms at the time of injury or shortly thereafter, rather than the current level of functioning. VA will not require that the TBI meet all the criteria listed under a certain severity level in order to classify the TBI at that severity level. If a TBI meets the criteria in more than one category of severity, then VA will rank the TBI at the highest level in which a criterion is met, except where the qualifying criterion is the same at both levels.
(Authority: 38 U.S.C. 501, 1110 and 1131)
[44 FR 50340, Aug. 28, 1979, as amended at 66 FR 18198, Apr. 6, 2001; 71 FR 52747, Sept. 7, 2006; 78 FR 76208, Dec. 17, 2013]
Related references
- 38 CFR § 3.303: VA service connection explained
- 38 CFR § 3.159: VA duty to assist: records and examinations
- 38 CFR § 3.300: Tobacco-Related VA Claims and Other Causes
- 38 USC § 1110: Wartime disability compensation eligibility
- 38 CFR § 4.1: What a VA disability rating measures
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