Spicer v. McDonough and the "But-For" Standard: What the May 2026 M21-1 Update Means for Your Secondary VA Claim
- 1.What Is Secondary Service Connection?
- 2.What Spicer v. McDonough Actually Decided
- 3.The Old Standard vs. the New Standard
- 4.The May 2026 M21-1 Update: What VA Raters Now Follow
- 5.How the Board Is Already Applying Spicer
- 6.What This Means for Your Nexus Letter
- 7.What Didn't Change
- 8.What You Should Do Right Now
- 9.Need Help With a Secondary Claim Under the New Spicer Standard?
- 10.Frequently Asked Questions
⚠️ KEY TAKEAWAY
On May 1, 2026, the VA updated M21-1 to reflect the Federal Circuit's Spicer v. McDonough ruling. The causation standard for secondary service connection shifted from "proximate cause" to "but-for cause." Veterans filing secondary claims now have three pathways: direct causation, aggravation, and a new treatment-interference pathway where the service-connected condition delayed, prevented, or interfered with treatment for a non-service-connected condition.
On May 1, 2026, the VA updated its M21-1 Adjudication Procedures Manual — the rulebook that VA raters use every day to decide disability claims. The update landed in Part V, Subpart ii, Chapter 2, Section D, the section governing secondary service connection and aggravation of non-service-connected disabilities. The changes stem from a Federal Circuit Court ruling called Spicer v. McDonough, 61 F.4th 1360 (Fed. Cir. 2023), and they shift the causation standard from "proximate cause" to "but-for cause."
If you have a secondary claim or are thinking about filing one - this matters. Here is what changed, what stayed the same, and how it affects the medical evidence you need.
What Is Secondary Service Connection?
Before we get into Spicer, let's make sure we're on the same page about secondary service connection under 38 C.F.R. § 3.310.
You don't have to prove that every condition you have was directly caused by your military service. If you already have a service-connected (SC) disability, and that SC disability causes or worsens a different condition, the second condition can also be service-connected. That's secondary service connection.
There are two flavors:
Secondary causation (§ 3.310(a)): Your SC condition caused a new condition. Example: service-connected diabetes causes peripheral neuropathy.
Secondary aggravation (§ 3.310(b)): Your SC condition made an existing non-service-connected condition worse beyond its natural progression. Example: service-connected PTSD worsens pre-existing hypertension through chronic stress and cortisol dysregulation.
Both have been available to veterans for years. The aggravation pathway was formalized in the 2006 regulation update, codifying the Court's decision in Allen v. Brown, 7 Vet. App. 439 (1995). None of that went away. What changed is how the VA evaluates the causal link.
What Spicer v. McDonough Actually Decided
Luther Spicer was a veteran with service-connected leukemia. His leukemia required chemotherapy. The chemotherapy prevented him from undergoing knee replacement surgery that could have improved his bilateral knee arthritis. Over time, his knees got worse — not because the cancer or chemo attacked his knees, but because the treatment for his SC condition blocked the fix.
Mr. Spicer filed a secondary service connection claim. The VA denied it. The Board denied it. The CAVC denied it with a divided panel. The majority said there was no "actual but-for causation" because they couldn't say his current knee condition wouldn't exist without the cancer.
Mr. Spicer appealed to the Federal Circuit. The Federal Circuit reversed and ruled in his favor.
The Court's Three Key Holdings1. The "but-for causation" standard in 38 U.S.C. § 1110 is not limited to a single direct cause-and-effect. It contemplates multi-causal links, including both action and inaction.
2. The broad language of § 1110 applies to conditions that would have been less severe were it not for the service-connected disability — including cases where the SC condition impeded treatment.
3. 38 C.F.R. § 3.310(b), the regulation controlling secondary aggravation, is unlawful because it imposes a "proximate cause" requirement stricter than what the statute demands.
The Old Standard vs. the New Standard
Before Spicer (Proximate Cause) | After Spicer (But-For Cause) |
|---|---|
"Did the SC condition directly cause or directly worsen the second condition?" | "Would this condition be less severe today but for the SC disability?" |
Required tight, identifiable physiological mechanism linking A to B | Allows multi-causal chains, medication effects, and treatment interference |
If no direct pathophysiological chain → claim often failed | SC condition can be relevant by delaying, preventing, or interfering with treatment |
Two pathways: causation and aggravation | Three pathways: causation, aggravation, and treatment interference |
The May 2026 M21-1 Update: What VA Raters Now Follow
The M21-1 is VA's internal procedures manual. When the Federal Circuit strikes down a regulation, VA eventually updates the M21-1 to reflect the new legal standard. That happened on May 1, 2026, in Part V, Subpart ii, Chapter 2, Section D.
The updated M21-1 now instructs raters that:
Four Changes in the M21-1 Update:
1. Treatment interference is recognized. A secondary claim may be valid when a SC condition interfered with, impeded, delayed, or prevented treatment for a non-service-connected condition.
2. Permanent worsening is not required. You do not have to show that the aggravation is permanent to establish secondary service connection.
3. Negative causation ≠ case closed. If a C&P examiner says "not caused by," they must also address whether the SC condition aggravated the secondary condition or interfered with its treatment.
4. Multi-causal chains are valid. A chain — for example, SC PTSD → weight gain → obesity → sleep apnea — can satisfy the but-for test if supported by medical evidence.
How the Board Is Already Applying Spicer
The Board of Veterans' Appeals has been citing Spicer in decisions since 2023. Here are patterns emerging from actual BVA rulings:
February 20, 2025 Sleep apnea secondary to tinnitus: Granted. The Board found that the veteran's service-connected tinnitus interfered with his ability to use a CPAP machine, directly citing Spicer for the principle that service connection may be warranted when a service-connected disability precludes treatment for a non-service-connected condition. The C&P examiner had acknowledged that tinnitus makes it difficult to get a good night's sleep and can compound problems with sleep apnea. The Board applied the benefit-of-the-doubt doctrine and granted secondary service connection.
June 4, 2025 Diabetes secondary to obstructive sleep apnea: Granted. The Board explicitly cited Spicer, 61 F.4th at 1364, holding that "the but-for causation standard is not limited to a single cause and effect, but rather contemplates multi-causal links, including action and inaction." The Board found that service-connected OSA did not need to be the sole cause of the diabetes — only that it was at least as likely as not a cause.
What This Means for Your Nexus Letter
A nexus letter is a medical opinion that connects your claimed condition to your service-connected disability. Under the Spicer framework, that medical opinion now has three distinct pathways to address — not just one or two.
Pathway 1 — Direct Secondary Causation
"It is at least as likely as not that [Condition B] was caused by [SC Condition A]." This is the traditional argument. Nothing changed here.
Pathway 2 — Secondary Aggravation
"It is at least as likely as not that [Condition B] was aggravated beyond its natural progression by [SC Condition A]." This existed before, but the standard is now but-for, not proximate cause. The opinion should establish a baseline severity level and explain the mechanism of worsening.
Pathway 3 — Treatment Interference (New Under Spicer)
"It is at least as likely as not that [Condition B] would be less severe today but for [SC Condition A], including because [SC Condition A] delayed, prevented, limited, or interfered with effective treatment for [Condition B]."
A strong nexus letter should address all applicable pathways. If the facts support it, a clinician should explain not only whether Condition A caused or worsened Condition B, but also whether Condition A blocked the veteran from getting treatment that would have reduced the severity of Condition B.
Sample Nexus Language — Treatment Interference Pathway"It is my medical opinion, to at least a 50 percent degree of probability, that Mr. [Name]'s bilateral knee osteoarthritis would be less severe today but for his service-connected [condition]. Specifically, his service-connected [condition] and its treatment with [medication/therapy] prevented him from undergoing [specific treatment] during the period from [date] to [date]. Peer-reviewed literature supports that [specific treatment] reduces pain and improves functional outcomes in patients with bilateral knee osteoarthritis (cite: [journal reference]). Because this treatment was unavailable due to the service-connected disability, the veteran's knee condition progressed beyond what would have been expected with appropriate intervention."
What Didn't Change
Secondary claims were not eliminated. 38 C.F.R. § 3.310 still exists. Secondary service connection — both causation and aggravation — is still available.
The standard of proof didn't change. "At least as likely as not" (50 percent or greater probability) is still the veteran-friendly standard.
You still need evidence. A broader legal standard does not mean unsupported claims will succeed. If anything, the broader standard requires more specific medical evidence explaining the but-for mechanism.
The three elements of secondary service connection are the same: (1) a current diagnosis, (2) a service-connected primary disability, and (3) a nexus — a medical link — between the two.
What You Should Do Right Now
If you have a pending secondary claim: Make sure your nexus letter addresses all three pathways — causation, aggravation, and treatment interference — where the facts support them. If your current nexus letter only addresses direct causation, it may be leaving arguments on the table.
If you were previously denied: Spicer may open the door to a Supplemental Claim with new and relevant evidence. A new nexus letter written under the but-for standard, addressing treatment interference or multi-causal chains not previously analyzed, could constitute the "new and relevant" evidence needed.
If you thought you couldn't prove direct causation: The but-for standard is broader than proximate cause. Conditions where the SC disability interfered with treatment — rather than directly causing the problem — may now be viable.
For any secondary claim: Work with a clinician who understands Spicer and can write a nexus opinion that directly addresses the but-for question with supporting medical literature and a clear mechanism explanation.
Need Help With a Secondary Claim Under the New Spicer Standard?
Military Disability Nexus provides clinician-written nexus letters, IMOs, DBQs, and Claim Readiness Reviews. Our clinical team writes opinions that address causation, aggravation, and treatment interference under the current framework.
OR
Frequently Asked Questions
What did Spicer v. McDonough change about secondary VA claims?
Spicer changed the causation standard from "proximate cause" to "but-for cause." The VA must now consider whether a condition would be less severe today but for the service-connected disability — including cases where the SC condition interfered with, delayed, or prevented treatment for a non-service-connected condition. The Federal Circuit also struck down 38 C.F.R. § 3.310(b) as unlawful.
What is "but-for causation" in VA disability claims?
But-for causation asks: "Would this condition exist — or be this severe — but for the veteran's service-connected disability?" This is broader than the old proximate-cause standard, which required a direct physiological link. Under but-for causation, multi-causal chains and treatment interference are recognized pathways.
What is the treatment-interference pathway?
Treatment interference allows secondary service connection when a SC disability delayed, prevented, or interfered with effective treatment for a non-service-connected condition. For example, a veteran whose SC heart condition prevented knee replacement surgery could claim the worsened knee — because the SC condition blocked the fix. That's Spicer's actual fact pattern.
When did the VA update M21-1 for Spicer?
The VA updated M21-1, Part V, Subpart ii, Chapter 2, Section D on May 1, 2026. The update instructs raters to apply the but-for standard, recognize treatment-interference claims, and ensure negative causation opinions also address aggravation.
Can I file a Supplemental Claim using Spicer?
Yes. If your secondary claim was denied under the old proximate-cause standard, a new nexus letter written under the but-for standard — addressing treatment interference or multi-causal chains not previously analyzed — can constitute "new and relevant" evidence for a Supplemental Claim.
How should my nexus letter address the but-for standard?
After Spicer, a strong nexus letter should address three pathways where supported: (1) direct secondary causation, (2) secondary aggravation with baseline evidence, and (3) treatment interference — explaining how the SC disability delayed, prevented, or interfered with treatment. Each pathway should include peer-reviewed citations and veteran-specific reasoning.
Need help with your VA claim?
Get expert guidance and documentation from our licensed clinicians
Get Free ConsultationDr. Kishan Bhalani is a subject matter expert on VA disability claims documentation, with more than five years of focused work at the intersection of clinical m…
Dr. Kishan Bhalani is a subject matter expert on VA disability claims documentation, with more than five years of focused work at the intersection of clinical m…
Originally published May 28, 2026 • Last updated May 28, 2026