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Nexus letter guide · 9411

Nexus Letter for PTSD: What It Must Say

The medical opinion connecting PTSD (9411) to your service is the piece of the file a rater weighs most heavily. This is what that letter has to contain — and a complete, real example you can read before writing a word.

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Key facts

Rated under
38 CFR Part 4, DC 9411 / 9434
Diagnostic code
9411
The standard
“At least as likely as not” — 50% or greater
Connection theories
Direct (§§ 3.303, 3.304(f))

The short answer

A nexus letter for PTSD is a medical opinion from a psychiatrist or psychologist saying your PTSD is "at least as likely as not" (a 50 percent or greater chance) caused by a specific stressor from your service. PTSD has its own rule, 38 C.F.R. § 3.304(f): VA needs a diagnosis that meets DSM-5 (§ 4.125(a)), medical evidence linking your current symptoms to an in-service stressor, and evidence that the stressor happened. So a PTSD letter has to name the diagnosis, name the stressor, and explain how that stressor produced the symptoms your records show. For many combat and fear-based stressors, VA's own exam does much of this work. A private opinion matters most when the link is disputed, when VA's exam went against you, or for military sexual trauma.

What a nexus letter is

A nexus letter is a written medical opinion from a licensed clinician stating that a veteran’s condition is “at least as likely as not” (a 50 percent or greater probability) connected to their military service — or to a condition already service-connected. It is the bridge between a diagnosis and service connection: the VA has your diagnosis and your service records, and the nexus opinion is what ties them together with medical reasoning a rater can weigh.

The standard · 38 CFR § 3.102

“At least as likely as not”

The opinion does not have to be certain, or even “more likely than not.” A 50 percent or greater probability meets the standard; when the evidence is in approximate balance, the benefit of the doubt goes to the veteran.

What a PTSD nexus letter must contain

  1. 1

    The diagnosis, by name and code

    PTSD named as a current, documented diagnosis — the condition the VA rates under 38 CFR Part 4, DC 9411 / 9434 (9411). No diagnosis, no service connection: the opinion has to be about a condition that exists in your records.

  2. 2

    The theory of connection

    For most PTSD claims this is direct service connection under 38 C.F.R. § 3.303 — the letter connects the condition to an in-service event, injury, or exposure, and says so explicitly.

  3. 3

    The magic words, used correctly

    The opinion must be stated to the VA's own standard: "at least as likely as not (a 50 percent or greater probability)." Weaker hedges like "possibly" or "may be related" fail; the standard is a specific legal threshold, and letters that don't invoke it get discounted.

  4. 4

    A rationale, not a conclusion

    The most common fatal flaw is the conclusory letter — an opinion with no reasoning. A rater is instructed to weigh the rationale: what in the records supports the connection, what the medical literature says about the mechanism, and why known alternative causes don't displace it. For PTSD specifically: The picture on your WORST days, in specific scenes — how often the panic hits, what a week of sleep looks like, what it has cost at work and at home; a statement that minimizes gets the lower level.

  5. 5

    A licensed clinician's signature and credentials

    The letter is medical evidence only when a licensed clinician — opining within their specialty — reviews it, exercises independent judgment, and signs it with their credentials. VA Claim Commander drafts the letter from your records and your story; your clinician signs it. An unsigned draft is a draft.

What a rater looks for in a PTSD nexus letter

  • A diagnosis that meets DSM-5

    Under 38 C.F.R. § 4.125(a), a mental health diagnosis has to conform to DSM-5. The letter should state the PTSD diagnosis and how it was reached (for example, a clinical interview and standard testing), not just list symptoms.

  • A named stressor, tied to service

    The opinion has to connect your symptoms to a specific in-service stressor: what happened, roughly when and where. "Military service" in general is not a stressor a rater can weigh.

  • Why this stressor explains these symptoms

    Nightmares about a specific event, avoidance of reminders, startle and hypervigilance that began after it. The reasoning should walk from the event to the symptoms in your treatment records.

  • The other explanations addressed

    Trauma before or after service, other diagnoses such as depression or substance use, and what came first. A strong letter deals with these instead of ignoring them.

  • The right kind of clinician

    A psychiatrist or psychologist who reviewed your records and, ideally, evaluated you. VA treats both as qualified to diagnose PTSD. The weight comes from the reasoning, not the title.

Direct service connection for PTSD

PTSD is usually claimed directly, under 38 C.F.R. § 3.304(f). The regulation sets out how the stressor itself can be shown, and that changes what a nexus letter needs to do:

  • Combat stressors (§ 3.304(f)(2))

    If you engaged in combat and the stressor fits the circumstances of your service, your own statement can establish it. The medical link still has to come from a clinician.

  • Fear of hostile military or terrorist activity (§ 3.304(f)(3))

    Here a VA psychiatrist or psychologist, or one VA contracts with, has to confirm the stressor is adequate for the diagnosis. That confirmation comes from VA's exam, so a private opinion supports it rather than replacing it.

  • Military sexual trauma and personal assault (§ 3.304(f)(5))

    Evidence from outside service records counts, including changes in behavior after the event. A clinician's opinion can explain what those changes indicate.

  • Other stressors

    For other in-service events, VA looks for credible evidence the stressor happened: records, buddy statements, or other documents. The nexus letter connects that event to your diagnosis.

Conditions often claimed secondary to PTSD

Once PTSD is service-connected, conditions it causes or makes worse can be claimed under 38 C.F.R. § 3.310. Each one needs its own nexus opinion explaining that link.

Why nexus letters fail

  • Conclusory: an opinion with no rationale. The rater is told to weigh reasoning, and a bare “it’s related” weighs nothing.
  • Wrong standard: “may be related” or “possibly caused by” instead of “at least as likely as not.”
  • Ignores the other causes: a strong letter names the recognized non-service risk factors and explains why they don’t displace the service connection.
  • Outside the specialty: a clinician opining far from their field gets less weight than one whose practice covers the condition.
  • Unsigned: a draft nobody signed is not medical evidence — it is homework.

Who can write a PTSD nexus letter

A psychiatrist or a psychologist. VA treats both as qualified to diagnose PTSD, and a mental health diagnosis has to conform to DSM-5 (38 C.F.R. § 4.125(a)). VA's own initial PTSD exams are done by a psychiatrist or a doctorate-level psychologist, so an outside opinion from the same kind of clinician meets the examiner on equal footing.

The best place to start is usually your own treating mental health provider, who already knows your history. VA Claim Commander drafts the letter from your records and your own words, so your clinician starts from a complete draft; they review it, change what they disagree with, and sign only if it is their opinion.

Commander Health, the clinician service we work with, handles physical conditions only. It does not write PTSD or other mental health opinions.

Common questions

Do I need a nexus letter for a PTSD VA claim?

If service connection isn't already established for PTSD, a medical nexus opinion is usually the piece a rater weighs most heavily. It connects the diagnosis (9411, 9400, 9403, 9404, 9410, 9412, 9413, 9416, 9417, 9421, 9431, 9432, 9433, 9434, 9435, 9440) to your service — or to an already service-connected condition — using the "at least as likely as not" standard. Presumptive claims are the main exception.

What must a nexus letter for PTSD say?

Four things: the current diagnosis by name and diagnostic code; the connection theory (direct under 38 C.F.R. § 3.303, or secondary under § 3.310); the opinion stated to the "at least as likely as not (50 percent or greater probability)" standard; and a medical rationale grounded in your records and the medical literature — not a bare conclusion. It must be signed by a licensed clinician.

Who can write a nexus letter for PTSD?

A psychiatrist or psychologist is the right author for a PTSD opinion. VA treats both as qualified to diagnose PTSD, and VA's own initial PTSD exams are done by a psychiatrist or a doctorate-level psychologist. Your treating mental health provider, who already knows your history, is often the best place to start. Commander Health, the clinician service we work with, handles physical conditions only and does not write PTSD or other mental health opinions.

Do I need a nexus letter for PTSD if VA gives me an exam?

Not always. For combat and fear-based stressors, VA's own examiner often decides the link. A private opinion from your psychiatrist or psychologist matters most when the VA exam was negative or thin, when the stressor link is disputed, or when the claim is based on military sexual trauma.

Does a PTSD nexus letter have to name the stressor?

Yes. The opinion has to tie your symptoms to a specific in-service stressor. Under 38 C.F.R. § 3.304(f), VA also needs evidence the stressor happened, and how that is shown depends on the type of stressor.

How does VA rate PTSD?

PTSD is rated under DC 9411 using the General Rating Formula for Mental Disorders in 38 C.F.R. § 4.130, at 0, 10, 30, 50, 70, or 100 percent, based on how much the symptoms impair work and social functioning. The nexus letter decides service connection; the rating is based on those criteria.

What conditions can be claimed secondary to PTSD?

Veterans commonly file sleep apnea, hypertension, GERD, erectile dysfunction, migraines, and depression secondary to service-connected PTSD under 38 C.F.R. § 3.310. Each one needs its own medical opinion explaining how PTSD caused it or made it worse.

How the VA rates PTSD →PTSD research library →PTSD rating criteria: 30, 50, 70, 100 →How VA rates mental health →VA disability calculator →

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