Traumatic brain injury (TBI) is a leading cause of death and long-term disability worldwide, arising from an external mechanical force that disrupts normal brain function. TBI ranges from mild concussion to severe injury with persistent neurological deficits. Beyond focal damage to neurons and vasculature, TBI triggers systemic and neuroendocrine changes that shape recovery. A central concept in modern TBI science is that injury perturbs the body’s stress-response systems, including the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic nervous system, and inflammatory signaling networks. These alterations can influence cognition, mood, sleep, autonomic function, and physical rehabilitation outcomes.
At the mechanistic level, TBI initiates both immediate and delayed cascades. The primary injury reflects the initial mechanical forces—such as acceleration-deceleration, rotational strain, and impact—leading to axonal stretching, membrane disruption, and ionic flux. The secondary injury phase involves progressive biochemical and cellular processes: excitotoxicity (excess glutamate), dysregulated calcium homeostasis, mitochondrial dysfunction, oxidative stress, neuroinflammation, blood-brain barrier (BBB) disruption, and microglial activation. These CNS events are tightly coupled to systemic responses. For example, BBB impairment and peripheral immune activation can drive cytokine signaling (e.g., interleukin pathways, tumor necrosis factor-related signals) that affects brain network function and peripheral physiology.
The stress response after TBI is clinically meaningful. HPA-axis dysregulation can result in abnormal cortisol dynamics. Cortisol is not simply a “stress hormone”; it orchestrates metabolic adaptation and modulates immune activity. After brain injury, patterns of cortisol release may be blunted, delayed, or otherwise maladaptive depending on injury severity, timing, and individual biology. Sympathetic overactivity can contribute to tachycardia, altered blood pressure regulation, sleep-wake disruption, and heightened perceived stress. Together, neuroendocrine and autonomic dysregulation can worsen fatigue, anxiety-like symptoms, and cognitive inefficiency, while also interfering with the neuroplasticity required for functional recovery.
Psychiatric and behavioral sequelae often track these mechanisms. While TBI is not synonymous with a single psychiatric diagnosis, there is a well-established association between TBI and increased risk of depression, anxiety disorders, post-traumatic stress symptoms, irritability, and cognitive-emotional dysregulation. These outcomes are influenced by lesion burden, diffuse axonal injury patterns, prior mental health, social support, and early physiologic stress markers. In addition, persistent inflammation and altered neurotransmission (including changes in monoaminergic systems such as serotonin and norepinephrine) may contribute to sustained mood symptoms.
Recovery after TBI is therefore best conceptualized as a biopsychosocial process supported by biologic repair and adaptive behavior. Neurorehabilitation aims to restore function through mechanisms including activity-dependent plasticity, motor learning, cognitive engagement, and graded exposure to meaningful tasks. However, physiologic stress dysregulation can limit the effectiveness of rehabilitation by reducing sleep quality, increasing pain and fatigue perception, and impairing attention and learning. Personalized rehabilitation strategies seek to tailor intensity, timing, and modality based on individual risk factors and biologic trajectories rather than adopting a one-size-fits-all protocol.
Personalization can include selecting interventions that explicitly account for stress physiology. Clinicians may integrate sleep optimization, symptom monitoring, and behavioral therapies that improve emotion regulation and reduce maladaptive stress responses. Where appropriate, management of comorbid conditions—such as chronic pain, insomnia, and mood disorders—can improve participation in therapies. From a research perspective, advances in biomarker-driven stratification aim to identify which patients exhibit prominent stress-response dysregulation (e.g., HPA-axis abnormalities or inflammatory signatures) and may therefore benefit from targeted approaches. Potential targets under investigation include anti-inflammatory pathways, interventions supporting autonomic stability, and strategies to modulate neuroendocrine responses.
In summary, traumatic brain injury produces both local brain damage and systemic stress-response dysregulation. The interplay between HPA-axis changes, autonomic imbalance, inflammatory signaling, and neuroplasticity helps explain variability in recovery, including cognitive and emotional outcomes. Modern rehabilitation increasingly emphasizes individualized treatment plans grounded in physiologic and clinical markers, with the goal of improving long-term function and quality of life.
Source: @USFNeurosurgery
University of South Florida Neurosurgery: Congratulations to Theresa Currier Thomas, PhD, on receiving a $2.85M NIH/NINDS R01 grant to advance traumatic brain injury (TBI) research.🎉 Her work explores how TBI affects the body’s stress response and recovery, paving the way for more personalized rehabilitation strategies.. #breaking
— @USFNeurosurgery May 1, 2026
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