HRV and interoception are two different measurements, not one
Heart rate variability is a measure of how much the gap between heartbeats naturally varies. A heart that speeds up and slows down flexibly from beat to beat is generally taken as a sign of a well-regulated autonomic nervous system — the automatic machinery that controls breathing, heart rate and digestion. Interoception is something else: the perception and interpretation of signals coming from inside the body, such as heartbeat, breath or hunger [5]. You can have low HRV and still sense your heartbeat accurately, or the reverse. Treating one as a stand-in for the other is an assumption, not a measurement.
That distinction matters for the question. If HRV were a reliable marker of interoceptive disturbance, you would expect studies to measure both in the same people and show they move together. The PTSD studies measure HRV and PTSD symptoms; the interoception study measures HRV and interoceptive accuracy in healthy volunteers [5]. No study here puts all three — PTSD, HRV and interoception — in the same participants.
What the PTSD studies actually show about HRV
The PTSD evidence is real, but it is about symptoms and autonomic function, not about internal-body perception. In a study of 169 World Trade Center responders followed with surveys three times a day for four days plus ambulatory heart monitoring, PTSD symptoms in one five-hour window predicted lower HRV in the next window, and the result held after adjusting for age, current heart problems and PTSD diagnosis [1]. Notably, the reverse did not happen: HRV did not predict later PTSD symptoms [1]. That timing is useful — it suggests symptoms may drive autonomic changes over hours, at least in this group, rather than the other way round.
A second study, in 53 women after pregnancy loss, found that PTSD severity scores were associated with HRV indices taken during a deep-breathing test, and that one index (SDNN, a measure of overall beat-to-beat variation) distinguished women with PTSD from those without with reasonable accuracy [3]. But here the direction is worth pausing on: women with PTSD had higher, not lower, SDNN, RMSSD and pNN50 values than women without PTSD, even though average heart rate was similar [3]. That runs against the common summary that PTSD means lower HRV, and it comes from a specific measurement condition — deep breathing — in a specific group.
A review-style paper on trauma and HRV notes that many studies report lower HRV in people with PTSD than in healthy controls, and that some work links greater symptom severity to lower HRV; it also raises the possibility that the age at which a first trauma occurs could shape this relationship, given links between the prefrontal cortex and HRV [4]. These are presented as possibilities and background, not as settled findings. Taken together, the PTSD studies support a link between PTSD symptoms and autonomic function, with the strength and even the direction depending on the population and how HRV was recorded.
The one study that measured interoception didn't include PTSD
The clearest evidence on HRV and interoception comes from a study of 25 healthy adults given eight weeks of HRV biofeedback — a training method where people learn to breathe in a way that boosts heart rate variability. After training, resting autonomic function changed: breathing rate fell, and respiratory sinus arrhythmia (the natural speeding and slowing of heart rate with breathing) and baroreflex sensitivity rose. Interoceptive accuracy, measured with a heartbeat-counting task, improved modestly, and self-reported interoceptive awareness changed, most of all on a 'self-regulation' subscale [5].
The important detail is the last one: the associations between the physiological changes and the interoceptive changes were modest, and the authors say more work is needed to clarify how autonomic regulation and interoceptive function relate [5]. So even in healthy adults, where both were measured directly, HRV and interoception did not move in tight lockstep. That weakens the idea that an HRV reading can stand in for an interoception reading — and this study did not involve PTSD at all.
What you can and cannot conclude from an HRV reading
For a clinician or researcher, the practical upshot is that HRV can reasonably be used as an indicator of autonomic function in PTSD, and there is evidence that PTSD symptoms and HRV are linked over short time spans [1][3]. It should not be presented as a proxy for interoceptive disturbance, because no study here tests that link in people with PTSD. A paper discussing interoceptive, body-oriented therapies for trauma raises the idea that such therapies address a core clinical issue in PTSD, but it does not supply HRV data tying interoception to autonomic measures [2].
The honest summary is a gap rather than a contradiction: the PTSD–HRV link and the HRV–interoception link have each been examined, in different samples, and the bridge between them has not been built. Reliable use of HRV as an interoceptive marker in PTSD would need studies measuring PTSD symptoms, HRV and interoceptive accuracy in the same people — and, given that direction and size of HRV effects varied across the PTSD studies here [1][3], it would also need to account for how and when HRV is recorded.
Sources used in this answer
Effects of Daily Posttraumatic Stress Disorder Symptoms on Heart Rate Variability
In 169 World Trade Center responders, PTSD symptoms in one five-hour interval predicted reduced HRV in the next interval, while HRV did not predict later PTSD symptoms.
Heart rate variability and posttraumatic stress disorder
The paper discusses HRV alongside baroreflex measures and PTSD symptoms and notes an argument that interoceptive body-oriented therapies can address a core clinical issue in PTSD, without directly testing HRV against interoception.
Heart Rate Variability Indices as Possible Biomarkers for the Severity of Post-traumatic Stress Disorder Following Pregnancy Loss
In 53 women after pregnancy loss, PTSD severity was associated with HRV indices during deep breathing, and women with PTSD showed higher SDNN, RMSSD and pNN50 values than those without.
Trauma Symptomatology and Heart Rate Variability
The paper reviews evidence that people with PTSD tend to have lower HRV than healthy controls and proposes that the age of first trauma exposure may modulate the trauma–HRV relationship.
Physiological correlates of interoception and the effect of heart rate variability biofeedback
In 25 healthy adults, eight weeks of HRV biofeedback changed autonomic measures and modestly improved interoceptive accuracy and awareness, but associations between physiological and interoceptive changes were modest.