How the conditions may be related
Prazosin, the first-line alpha-1 adrenergic blocker prescribed for PTSD-related nightmares, produces orthostatic hypotension as a direct pharmacological effect. Alpha-1 blockade reduces peripheral vascular resistance and impairs the compensatory vasoconstriction normally triggered by standing, causing blood pressure drops of 20+ mmHg systolic upon position change. Military-age veterans often tolerate higher doses for nightmare suppression, increasing orthostatic risk. Syncope (fainting) from prazosin-induced hypotension is a documented adverse effect occurring in 1-5% of patients at therapeutic doses. The resulting falls can cause secondary traumatic injuries. Other PTSD medications (trazodone, quetiapine, doxazosin) carry similar orthostatic risk.
“Disability which is proximately due to or the result of a service-connected disease or injury shall be service connected.”
A disability may qualify for secondary service connection when evidence shows that an existing service-connected condition caused it or increased its severity beyond natural progression. These are the causation and aggravation paths in 38 CFR § 3.310. Having both conditions does not, by itself, establish the connection.
Look at the evidence behind the pairing
- Raskind MA et al. (2003) Am J Psychiatry (prazosin for PTSD nightmares — efficacy and side effects)
- Singh B et al. (2016) Ann Pharmacother (prazosin-related hypotension in PTSD treatment)
- VA/DoD CPG for PTSD (2023) (medication management guidelines).
Strong, Moderate, and Emerging are research categories assigned within this library. They are not VA determinations, promises of service connection, or estimates of your approval chances. Read the supporting research and consider how it applies to your own history. Association between conditions does not, by itself, establish that one caused or aggravated the other.
Build the link to your own history
A nexus is the link between the two conditions. Relevant evidence can include medical records, a reasoned medical opinion, and, in some circumstances, lay evidence. A private nexus letter can help, but is not universally required. An opinion should explain how the evidence in your case supports causation or aggravation, rather than only naming a possible association.
VA may arrange a C&P examination or request a medical opinion when needed to decide an initial or Supplemental Claim. You can submit an opinion from a treating or independent clinician, but VA does not require everyone to purchase a private nexus letter. Its duty to assist does not guarantee a favorable opinion or a granted claim.
Pairing-specific research notes
Document prazosin or alpha-blocker prescription for PTSD treatment and dosage history. Blood pressure logs showing orthostatic drops. Emergency room records if syncope occurred. Prescribing psychiatrist nexus letter confirming the medication is for service-connected PTSD and that orthostatic hypotension is a recognized side effect. There is no diagnostic code for hypotension or for syncope: 38 CFR § 4.104 and § 4.124a carry neither as a listing at eCFR issue 2026-08-27. DC 7101 is hypertensive vascular disease and is not the analogous code for the opposite condition. An unlisted condition is rated by analogy under 38 CFR § 4.20 and § 4.27 to a closely related listed condition, and which one VA builds depends on the functions affected in your case, so ask your representative rather than filing under a code chosen here. Document dizziness, near-syncope, and fall risk impact on daily functioning.
A diagnosis does not guarantee an additional rating
A separately compensable secondary disability may receive its own evaluation, which VA combines with other ratings under 38 CFR § 4.25. Separate diagnoses do not always mean separate ratings: § 4.14 prohibits compensating the same manifestations more than once, and some body systems have additional rating rules. For aggravation, the compensable increase must account for the baseline severity.
The formula applies the whole-person concept: a 50% combined existing rating plus a new 30% rating yields 65% (rounded to 70%), not 80%.
This example starts with an unrounded combined value. If your current award was already rounded, use your individual ratings to calculate the new total. VA rounds to the nearest ten only after combining all applicable ratings.
Read the combined ratings ruleBoth causation and aggravation are forms of secondary service connection. Aggravation means an increase in severity attributable to a service-connected condition, beyond natural progression. Permanent worsening is not required under Ward v. Wilkie (2019). Section 3.310(b) also requires medical evidence establishing a baseline level of severity; VA deducts the baseline and any natural progression when determining the compensable increase.
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See how separately assigned ratings combine using VA math.
Open the calculatorSecondary claims, explained
What is a secondary service-connected condition?
A disability may qualify for secondary service connection when evidence shows that an existing service-connected condition caused it or increased its severity beyond natural progression. These are the causation and aggravation paths in 38 CFR § 3.310. Having both conditions does not, by itself, establish the connection.
What evidence can establish the connection?
A nexus is the link between the two conditions. Relevant evidence can include medical records, a reasoned medical opinion, and, in some circumstances, lay evidence. A private nexus letter can help, but is not universally required. An opinion should explain how the evidence in your case supports causation or aggravation, rather than only naming a possible association.
Do I have to pay for a private nexus letter?
VA may arrange a C&P examination or request a medical opinion when needed to decide an initial or Supplemental Claim. You can submit an opinion from a treating or independent clinician, but VA does not require everyone to purchase a private nexus letter. Its duty to assist does not guarantee a favorable opinion or a granted claim.
Does aggravation have to be permanent?
Both causation and aggravation are forms of secondary service connection. Aggravation means an increase in severity attributable to a service-connected condition, beyond natural progression. Permanent worsening is not required under Ward v. Wilkie (2019). Section 3.310(b) also requires medical evidence establishing a baseline level of severity; VA deducts the baseline and any natural progression when determining the compensable increase.
Will a secondary condition get a separate rating?
A separately compensable secondary disability may receive its own evaluation, which VA combines with other ratings under 38 CFR § 4.25. Separate diagnoses do not always mean separate ratings: § 4.14 prohibits compensating the same manifestations more than once, and some body systems have additional rating rules. For aggravation, the compensable increase must account for the baseline severity.
When can a secondary claim’s effective date begin?
An effective date generally depends on when VA received the claim and when entitlement arose, with exceptions. A qualifying intent to file may preserve an earlier claim date if VA receives the completed claim within one year. Review deadlines and continuous pursuit can affect the date; a prior denial does not automatically establish an earlier effective date.