The Neurobiology of Hyperarousal, the Stress Response, and the Challenge of Feeling Safe
I love the cozy season, it is a time snuggle up with a good book and rest. But what happens when your mind-body system won’t let you relax? You finally have time to slow down, but instead of feeling relaxed, you find yourself becoming increasingly restless. Your thoughts begin to race, your attention shifts from one concern to another, and you feel an almost automatic urge to stay busy. Rather than experiencing a sense of relief, stillness seems to bring an unexpected sense of unease
For some people, slowing down is surprisingly difficult.
This experience may be more than a habit or an inability to disconnect. Chronic stress can influence the brain's threat-detection systems, stress hormones, and autonomic nervous system in ways that make it difficult to transition from a state of vigilance into one of relaxation.
For individuals with a history of prolonged stress or developmental trauma, the experience can be particularly complicated. When the nervous system has adapted to an environment of unpredictability, staying alert may become a familiar way of navigating the world. In this context, rest may not immediately register as safety.
The Brain Under Chronic Stress
The brain is constantly evaluating information from the internal and external environment to determine whether a situation requires a response. This process involves several interconnected regions, including the amygdala, hippocampus, and prefrontal cortex.
The amygdala plays an important role in detecting emotionally significant information, including potential threats. The hippocampus contributes to contextual memory, helping the brain distinguish between present circumstances and previously experienced events. The prefrontal cortex supports executive functioning, attention, and the regulation of emotional responses.
Chronic stress can influence communication among these regions.
Research suggests that prolonged exposure to stress hormones and stress-related signaling can affect prefrontal cortical functioning, hippocampal plasticity, and amygdala reactivity. These changes are not uniform or necessarily permanent, but they may contribute to difficulties with emotional regulation and the ability to disengage from perceived threats.
When threat monitoring remains elevated, the brain may continue scanning for problems even when the immediate environment is relatively safe.
In other words, the body may be physically at rest while the brain remains psychologically on alert- meaning you won’t feel relaxed.
The HPA Axis: When the Stress Response Becomes Dysregulated
One of the central systems involved in the physiological stress response is the hypothalamic-pituitary-adrenal (HPA) axis.
When the brain detects a threat, the hypothalamus signals the pituitary gland, which stimulates the adrenal glands to release cortisol. Cortisol helps mobilize energy, regulate immune activity, and prepare the body to respond to demands.
This is an adaptive process. The stress response is not inherently harmful; it is essential for survival.
However, repeated or prolonged stress exposure can alter the regulation of this system. Some individuals demonstrate elevated cortisol activity, while others show flattened daily cortisol rhythms or reduced cortisol responses. There is no single hormonal pattern that characterizes everyone experiencing chronic stress or trauma.
These alterations may affect sleep, energy regulation, immune function, and emotional well-being.
When the stress-response system has difficulty shifting between activation and recovery, the transition into rest may become more challenging.
Why Stillness Can Feel Uncomfortable
For individuals who have experienced prolonged adversity, vigilance may have developed as an adaptive response.
Growing up in an unpredictable or emotionally unsafe environment can teach a child to monitor other people's moods, anticipate conflict, and remain alert to subtle changes in the environment. Over time, these behaviors may become deeply ingrained patterns of attention and physiological arousal.
As adults, some individuals may continue to experience a persistent sense of urgency, even when there is no immediate threat.
This can manifest as:
Difficulty sitting still or disengaging from work.
Feeling anxious when there is nothing to do.
Repeatedly checking messages, email, or other sources of stimulation.
Difficulty falling asleep despite physical exhaustion.
Feeling uncomfortable with silence or unstructured time.
Experiencing intrusive thoughts when external distractions disappear.
For some trauma survivors, slowing down can also increase awareness of internal sensations, emotions, or memories that were previously managed through activity and distraction.
Rest may therefore bring a person into contact with experiences that feel difficult to tolerate.
This does not mean that everyone who struggles to relax has experienced trauma. Anxiety, depression, sleep disorders, environmental demands, and other health conditions can also contribute to these patterns.
The Autonomic Nervous System and the Difficulty of Switching Off
The autonomic nervous system regulates many functions that occur without conscious effort, including heart rate, blood pressure, digestion, and aspects of respiratory function.
Its sympathetic branch helps mobilize the body during periods of demand, while parasympathetic pathways contribute to recovery, digestion, and other restorative processes.
These systems work together rather than operating as a simple on-off switch.
Under conditions of chronic stress, some individuals experience persistent sympathetic activation, including increased vigilance, muscle tension, and difficulty settling physiologically.
This can make it harder to move into a state conducive to sleep and restoration.
Importantly, relaxation is not simply the absence of activity. It involves a coordinated shift in physiological processes, attention, and perceived safety.
For someone accustomed to remaining alert, this transition may require time and repeated experiences of safety.
Why Distraction Can Become a Form of Regulation
Constant activity can sometimes serve as a way of managing uncomfortable internal states.
Working, exercising, scrolling, organizing, or staying busy may temporarily reduce awareness of anxiety or distress. These behaviors are not inherently unhealthy. In many circumstances, they are adaptive and useful.
However, when activity becomes the primary way a person regulates emotional discomfort, opportunities to develop tolerance for stillness may become limited.
The brain can learn through repetition. If distraction repeatedly reduces distress, the behavior may become reinforced. Over time, unstructured moments may begin to feel increasingly uncomfortable.
This is one reason why simply telling someone to slow down, meditate, or relax may not be particularly helpful.
For some people, the first step is not learning how to relax. It is developing a greater capacity to experience stillness without feeling overwhelmed.
Relearning How to Rest
The ability to rest can be approached as a capacity that develops through repeated experiences, rather than something that should happen automatically.
A trauma-informed approach may include:
1. Gradual exposure to stillness
Rather than attempting prolonged meditation or extended periods of inactivity, begin with brief, manageable experiences of quiet. This allows a person to develop tolerance without becoming overwhelmed.
2. Supporting physiological regulation
Slow, comfortable breathing, gentle movement, and attention to physical sensations may help some individuals regulate arousal. These practices should be adapted to the person's experience, particularly when focusing inward increases anxiety or dissociation.
3. Establishing predictable routines
Consistent sleep and wake times, regular meals, and predictable periods of activity and recovery can support circadian regulation and reduce unnecessary physiological demands.
4. Incorporating movement
Physical activity can support mood, sleep, and stress regulation. Walking, running, yoga, and other forms of movement may offer an accessible way to transition between periods of activation and recovery.
5. Developing relational safety
For individuals with developmental trauma, experiences of consistency, trust, and emotional safety within relationships can be important components of recovery. The therapeutic relationship may provide opportunities to experience connection without the same degree of vigilance or self-protection.
Rest Is a Biological and Psychological Process
Perhaps one of the most important things to understand about chronic stress is that difficulty relaxing is not necessarily a failure of willpower.
The ability to rest involves interconnected neural circuits, hormonal systems, autonomic regulation, sleep processes, and our perception of safety.
For people who have spent years adapting to unpredictable or threatening environments, slowing down may initially feel unfamiliar. The nervous system may have learned to prioritize vigilance because vigilance once served a protective purpose.
Recovery involves creating new experiences in which the absence of threat becomes increasingly recognizable.
Over time, through therapeutic work, supportive relationships, and practices that promote physiological regulation, individuals may develop greater flexibility in their stress responses.
The goal is not to eliminate the stress response. It is to regain the ability to move between activation and recovery as circumstances require.
Rest is not simply doing nothing. It is the capacity to experience a moment in which the mind and body no longer need to prepare for what might happen next.
References and Further Reading
McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338, 171–179. https://doi.org/10.1056/NEJM199801153380307
McEwen, B. S. (2007). Physiology and neurobiology of stress and adaptation: Central role of the brain. Physiological Reviews, 87(3), 873–904. https://doi.org/10.1152/physrev.00041.2006
Arnsten, A. F. T. (2009). Stress signalling pathways that impair prefrontal cortex structure and function. Nature Reviews Neuroscience, 10, 410–422. https://doi.org/10.1038/nrn2648
Thayer, J. F., & Lane, R. D. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 61(3), 201–216.
Katrina Anderson, PhD, LMHC
Integrative Psychotherapist | Trauma Specialist | Clinical Hypnotherapist
