A new study published in Translational Psychiatry is drawing attention to one of the most intriguing questions in fear research: why do some people begin to feel safer during a threatening experience while others remain trapped in escalating fear and avoidance? The research, led by C. Szeska, K. Klepzig, A. O. Hamm and colleagues, reports that cardiac vagal activity during exposure to threat is associated with the within-session inhibition of fear and avoidance. The finding links the heart’s parasympathetic regulation system with the brain’s ability to update danger predictions in real time.
Fear is designed to protect the body from harm. When the brain detects a possible threat, it rapidly mobilizes attention, defensive behavior and physiological arousal. Avoidance can be useful when danger is genuine, but it becomes problematic when it persists in situations that are objectively safe. In anxiety disorders, people may avoid places, objects, bodily sensations or social situations because their nervous system continues to treat them as dangerous. Exposure-based treatments work partly by allowing new learning to occur while the feared situation is experienced without the expected catastrophe.
The new paper focuses on what happens inside a single exposure session. Fear reduction is often measured across multiple treatment sessions, but researchers also observe shorter-term changes: a person may initially show a strong defensive response and then gradually become less fearful as the same situation continues. This process is known as within-session inhibition. It does not necessarily erase the original fear memory. Instead, it may reflect the formation of a competing safety representation that temporarily suppresses fear when the person remains in the threatening context.
The study’s central physiological marker is cardiac vagal activity, a measure related to the influence of the vagus nerve on heart function. The vagus nerve is a major component of the parasympathetic nervous system, which helps regulate the body after challenge and supports flexible shifts between activation and recovery. Cardiac vagal activity is commonly estimated from variations in the time interval between heartbeats, known as heart-rate variability. These beat-to-beat fluctuations are not random noise; they reflect the dynamic interaction between the heart, brain and autonomic nervous system.
During threat exposure, the heart may accelerate as the body prepares for action. Yet effective regulation does not mean that physiological activation disappears immediately. A flexible nervous system can respond strongly when danger is detected and then adjust as new information indicates that the situation is tolerable. By examining cardiac vagal activity while people are exposed to threat in vivo, the researchers investigated whether this regulatory flexibility is connected to reductions in fear and avoidance during the same experience.
The wording of the findings is important. The study identifies an association between cardiac vagal activity and within-session inhibition; it does not establish that vagal activity directly causes fear to decline. The relationship could reflect several interacting processes, including attention, perceived control, safety learning, emotion regulation or the ability to remain engaged with a difficult situation. Nevertheless, the result is significant because it places autonomic physiology at the center of a psychological process that is often described mainly in terms of cognition and behavior.
The distinction between fear and avoidance is also crucial. A person can report feeling afraid while still approaching a threatening situation, or they can avoid it before fear has a chance to change. Avoidance prevents the nervous system from receiving corrective information, allowing danger expectations to remain untested. If cardiac vagal activity is linked to the inhibition of both fear and avoidance, it may signal a broader capacity to stay present, process new evidence and resist the impulse to escape.
This perspective could eventually influence how clinicians monitor and personalize exposure-based interventions. Measures of cardiac vagal activity are non-invasive and can be collected through electrocardiography or wearable sensors, although their interpretation requires care. Heart-rate variability is affected by breathing, movement, posture, medication, fitness, sleep and many other factors. A physiological signal should therefore not be treated as a simple diagnostic score or a direct measurement of emotional strength. Its potential value may lie in tracking patterns over time and combining them with behavioral and subjective reports.
The findings also contribute to a larger scientific shift toward understanding fear as a body-wide process rather than a response generated by the brain alone. Threat learning involves neural circuits, hormones, muscles, breathing, cardiovascular regulation and behavior, all operating in continuous feedback. The heart does not independently determine whether a situation is safe, but its changing activity may reflect how successfully the organism is adapting as circumstances unfold. By studying that adaptation during real threat exposure, the researchers highlight the physiological foundation of safety learning.
For people affected by anxiety, the message is cautiously encouraging: the ability to remain in contact with a feared situation may be accompanied by measurable changes in the body’s regulatory systems. The study does not suggest that fear should simply be suppressed, nor that a single heart-based measure can explain recovery. Instead, it points toward a more precise understanding of why exposure sometimes produces rapid learning and why, in other cases, fear and avoidance remain stubbornly high. Future research will need to determine whether cardiac vagal activity can predict treatment response, strengthen safety learning or guide individualized interventions.
Subject of Research: Cardiac vagal activity during in-vivo threat exposure and its association with within-session inhibition of fear and avoidance
Article Title: Cardiac vagal activity during in-vivo threat exposure is associated with within-session inhibition of fear and avoidance
Article References: Szeska, C., Klepzig, K., Hamm, A.O. et al. Cardiac vagal activity during in-vivo threat exposure is associated with within-session inhibition of fear and avoidance. Transl Psychiatry 16, 388 (2026). https://doi.org/10.1038/s41398-026-04333-7
Image Credits: AI Generated
DOI: 10.1038/s41398-026-04333-7
Keywords: cardiac vagal activity, heart-rate variability, fear inhibition, avoidance, threat exposure, anxiety, exposure therapy, safety learning, autonomic nervous system
