Hyperarousal is not one thing - researchers identify seven distinct types

Clinicians and researchers have long used the word "hyperarousal" as though everyone agreed on what it meant. They do not. A sleep researcher studying insomnia, a trauma specialist treating PTSD, and a psychiatrist managing ADHD may all invoke hyperarousal - but they are often describing different physiological and psychological states. That ambiguity has quietly muddled both research and treatment for years.

A new study from the Netherlands Institute for Neuroscience set out to determine whether hyperarousal is genuinely one phenomenon or several. The answer: seven distinct types, each appearing across multiple disorders but in different proportions depending on the diagnosis.

Untangling a term that meant too many things

The research team, led by first author Tom Bresser, started with a simple observation. Hyperarousal plays a documented role in insomnia, depression, anxiety, panic disorder, PTSD, and ADHD. But the questionnaires used to assess these conditions each measured hyperarousal differently, making it impossible to compare findings across disorders.

To address this, the team combined a large number of questionnaires spanning multiple mental health conditions into one comprehensive survey. Nearly 500 participants recruited through sleepregister.nl completed the full battery of questions.

Statistical analysis revealed seven separable types of hyperarousal. Almost every type appeared in multiple disorders, but the relative severity of each type differed depending on the condition. A person with insomnia might show a particular pattern dominated by certain hyperarousal types, while someone with anxiety or PTSD would show a different distribution.

The specifics of each type - what distinguishes somatic vigilance from cognitive rumination from emotional reactivity, for instance - are detailed in the team's paper. The key insight is structural: hyperarousal is not a single dial turned up or down, but a dashboard of at least seven independent readings.

One questionnaire to replace many

Based on these findings, Bresser and colleagues developed a new, concise questionnaire designed to measure all seven types simultaneously. The practical advantage is significant. Instead of piecing together fragments from disorder-specific instruments, researchers can now use a single tool to map a patient's full hyperarousal profile.

The sleep lab at the Netherlands Institute for Neuroscience is already using the questionnaire in ongoing studies of insomnia and anxiety. It is freely available in the appendix of the published paper.

What this means for treatment

The clinical implications are potentially substantial, though still speculative at this stage. Bresser notes that patients often present with one diagnosed disorder but have underlying predispositions to others. A patient arriving with insomnia may also carry elevated scores on hyperarousal types more typically associated with anxiety or depression.

If clinicians could identify these overlapping hyperarousal patterns early, they might tailor treatment plans that address the most relevant types simultaneously rather than treating each disorder in isolation. Instead of focusing narrowly on insomnia, for example, a therapist might also target the specific hyperarousal pattern that predisposes a patient to anxiety.

That clinical application remains a future goal rather than a current reality. The questionnaire has not yet been validated in clinical treatment settings, and the study's participant pool, while nearly 500 strong, was drawn from a single Dutch sleep registry. Whether the seven-type framework holds across different populations and clinical contexts is an open question.

Mapping hyperarousal in the brain

Bresser is now investigating which brain regions correspond to each type of hyperarousal. The goal is to move from a purely questionnaire-based taxonomy to one grounded in neurobiology - understanding not just that seven types exist, but why they exist and what drives each one at the neural level.

This is slow, painstaking work. Brain imaging studies require careful design to isolate specific arousal states, and the overlap between types means that clean separations will be difficult. But if the brain-mapping effort succeeds, it could provide a biological foundation for the kind of targeted treatment the questionnaire is designed to enable.

The study's contribution is not a treatment or a cure. It is a better map. For a field that has been using a single word to describe at least seven different things, that clarity alone represents meaningful progress.