Walter Cannon's (1932) foundational description of the "fight-or-flight" response argues that the autonomic nervous system mobilises in response to perceived dangers. This produces physiological and behavioural states adapted for engagement or escape. Later, a third response was added: freezing, signified by immobility, reduced output, and resource conservation in the face of inescapable threats (Bracha, 2004). These three states are not psychiatric constructs. They are basic modes of the autonomic nervous system found across species.

When mapped against the seven phenotypes identified by Painter et al. (2025), the fit is conspicuous. The shutdown cluster, characterised by affective numbness, emptiness, and low arousal, responds closely to a frozen state. Motor output is reduced, emotional responsiveness is blunted, and the system appears to have entered a conservation mode. The Activation Cluster, in which patients report high energy alongside anxiety and nervous arousal, reflects the hyperactivated profile of a flight state: the thermostat running hot, using resources while scanning for threat. The anger clusters frustration, irritability, and overt anger maps directly onto fight activation; the nervous system directs energy outward in a state of resistance. The Distress Clusters, combining anxiety, sadness, and frustration, may represent oscillation between flight and freeze, consistent with the transition patterns detected in the original data set.

The Social Isolation Cluster warrants particular attention. Withdrawal from social contact is, in simple terms, a sign of the body freezing. It is shutting down from social interaction just when that interaction could help restore balance. This cluster is characterised by loneliness and grief, along with low intervention use. It is not paradoxical; it is predictable.

McEwen's (1998) concept of allostatic load, the cumulative physiological cost of chronic dysregulation, provides a structure for understanding why these states persist. The nervous system does not exclusively respond to current conditions; it calibrates around a learned baseline formed by prior experience. Long-term dysregulation or early experiences that create a heightened sense of threat can change the normal level of regulation. The system returns to its dysregulated setpoint regardless of what is presented to it from outside.

These events possess direct implications for treatment. Looking at long-term diary data from NeuroLog users shows that people with FND often stay in the same autonomic state, like shutdown or hyperarousal, for several days in a row, much more often than would happen by chance. This is not volitional persistence. It reflects the setpoint phenomenon: a system calibrated to a displaced baseline that returns to that baseline as its default.

Barrett's (2017) predictive processing account offers a complementary explanation. The brain constantly generates predictions about the body's internal state, updating them in light of incoming sensory evidence. In individuals whose prior experience has heavily weighted threat predictions, the system's generative model may default to alarm or shutdown even in objectively safe conditions. Symptoms are not errors in this account; they are the outputs of a prediction engine whose priors have been determined by experience into a configuration that no longer serves the individual well.

If FND emotional types reflect autonomic states rather than fixed traits or distinct reactions, multiple important clinical considerations occur. First, assessment may need to go beyond symptomatic subtyping. Knowing that a patient has functional gait disorders or seizures describes nervous system output. Realizing that these symptoms occur in chronic freeze or hyperaroused flight states clarifies the conditions that produce them. These clinical pictures differ, and their response to the same interventions may vary.

In the Second, the near-absence of intervention in the Anger and Activation groups and its sharp decline in the Shutdown group are logical. A nervous system in fight mode resists help by default. In flight, it is too busy scanning to engage. In freeze, it cannot access the motivation to seek or use help. These are state-dependent constraints, not attitudinal barriers. Timing and modality of intervention may matter as much as content.

And, the Resilience Cluster's fragility is notable. A substantial proportion of patients return to anxious or distressed states within days. This is consistent with a setpoint effect. Brief windows of regulation do not recalibrate the baseline. Sustained conditions of safety, co-regulation, and lowered demand may be required to shift the setpoint over time, rather than symptomatic interventions delivered against the current of an unaddressed regulatory baseline.