This article originally appeared in the Winter 2026 issue. Download the full issue here.
While conditions such as PTSD, depression, anxiety and burnout are real and prevalent, what is rarely addressed is the underlying physiology that can mimic, overlap, or exacerbate mental health conditions.
Disrupted sleep, endocrine abnormalities, nutrient deficiencies, brain injury, environmental exposures, and autonomic nervous system dysfunction all contribute to symptoms that overlap with psychiatric conditions. Without considering these biological underpinnings, providers risk misdiagnosis, under-treatment, or failure to recognize reversible contributors to distress, leaving firefighters insufficiently educated on the truth of what is happening in their minds and bodies.
Sleep Loss: The Master Amplifier
First responders work overnight shifts, 24-hour tours, or rotating schedules. Volunteers and paid on-call firefighters are routinely toned out in the middle of the night. All of this desynchronizes the body’s circadian rhythms. This circadian misalignment alters the secretion of melatonin, cortisol, and insulin, disrupting energy balance and stress responses.
Research shows that shift workers experience higher rates of insulin resistance and metabolic syndrome due to altered circadian regulation of glucose and lipid metabolism. Cortisol rhythms flatten in chronic night-shift workers, impairing stress recovery and mood regulation. Endocrine dysregulation translates directly into symptoms of fatigue, irritability, and poor concentration – all of which overlap with depression and burnout.
Thyroid dysfunction is another under-recognized consequence. Studies show more hypothyroidism in shift workers compared to day workers. Hypothyroidism produces low mood, cognitive slowing, and weight gain, which can easily be mistaken for psychiatric illness.
Sleep deprivation is a defining feature of first responder life. Sleep restriction alone produces significant cognitive deficits in memory, attention, and decision-making. Fragmented sleep impairs emotional regulation and increases impulsivity, mimicking symptoms of mood and anxiety disorders.
Chronic sleep loss is not only an amplifier of mental health problems but can itself masquerade as depression or generalized anxiety, creating diagnostic ambiguity. Effective evaluation of firefighters must therefore include sleep history and screening for sleep apnea or circadian rhythm disorders.
The autonomic nervous system (ANS) regulates heart rate, blood pressure, and stress reactivity. In first responders, chronic hypervigilance and repeated trauma exposures alter autonomic nervous system balance, often measurable through heart-rate variability (HRV).
Studies show significantly lower HRV in individuals with PTSD, reflecting impaired parasympathetic control. Reduced HRV is linked with symptoms of hyperarousal, panic, and poor sleep, again, overlapping with primary anxiety disorders. For firefighters who live in a state of readiness, ANS dysfunction can create chronic fight-or-flight physiology indistinguishable from anxiety disorders.
HRV is a powerful indicator of overall health, with a higher HRV score indicating better health. Screening HRV or simple orthostatic vitals may reveal underlying distress and guide targeted interventions, such as biofeedback, mindfulness, or vagal-stimulation techniques.
Nutritional Deficiencies
Firehouse meals and on-the-go eating habits create predictable nutrient gaps. Research among career firefighters found frequent under-consumption of vitamin D, magnesium, potassium, and vitamin E.
Deficiencies in these nutrients can manifest with fatigue, muscle weakness, irritability, and low mood. Vitamin D deficiency, in particular, has been linked to depression and impaired cognitive performance. Magnesium insufficiency contributes to sleep disturbances and heightened stress reactivity.
When a firefighter or medic presents with irritability, sleep issues, and poor concentration, the knee-jerk assumption may be depression or PTSD. But addressing diet and supplementation may alleviate symptoms prior to considering pharmacologic psychiatric treatment.
Smoke, CO, and PFAS
Firefighters are routinely exposed to toxins with neurological and endocrine effects. Firefighters inhale smoke containing carbon monoxide, which binds hemoglobin and limits oxygen delivery. Even subacute CO exposures can produce delayed neurocognitive symptoms such as memory loss, headache, and depression-like symptoms..
Additionally, firefighters have disproportionate exposure to PFAS from turnout gear and firefighting foams. PFAS are endocrine disruptors associated with thyroid dysfunction and metabolic abnormalities, and are highly suspected to be carcinogenic. Subclinical hypothyroid symptoms include fatigue, weight change, and cognitive slowing, again overlapping with depression.
Heat, Dehydration, and Electrolyte Disturbances
Working in high-heat environments with heavy gear increases the risk of dehydration and electrolyte imbalance among firefighters. Cognitive performance drops sharply when dehydrated, with slowed reaction times and mood changes. Overhydration without adequate sodium replacement can cause exercise-associated hyponatremia, leading to confusion, irritability, and even seizures, stressing the importance of hydrating with an electrolyte-rich beverage rather than plain water.
In the field, these physiological changes may present as acute agitation or cognitive dysfunction, easily mistaken for psychiatric breakdown. Recognizing hydration and electrolyte status is critical when evaluating mental health complaints during or after incidents.
Traumatic Brain Injury
First responders face the risk of traumatic brain injury through falling debris, motor vehicle crashes, falls, or blast exposures. Even mild traumatic brain injury produces cognitive deficits, irritability, and mood instability that overlap with psychiatric disorders. Without awareness, these neurodegenerative consequences may be misattributed to primary psychiatric illness or burnout.
5 To-Dos
Given the overlap between physiology and psychology, clinicians working with first responders should adopt a structured evaluation framework.
- History and Workload: Assess shift schedules, cumulative overtime, number of responses for volunteers, sleep patterns, head injuries, toxin exposures, and nutrition.
- Laboratory Screening: Basic metabolic panel, fasting glucose/A1c, thyroid function tests, morning cortisol, vitamin D, magnesium, and hormones such as testosterone.
- Sleep and Autonomics: Evaluate for sleep apnea, circadian rhythm disorders, HRV, and orthostatic vitals.
- Exposure-Specific Testing: Carboxyhemoglobin levels for CO, neurocognitive testing for TBI, thyroid screening for PFAS exposure.
- Multidisciplinary Referral: Integrate occupational medicine, sleep medicine, nutrition, sports-concussion clinics, and behavioral health.
This approach ensures reversible biological contributors are ruled out before assigning purely psychiatric diagnoses.
Policy and Cultural Implications
Addressing physiology is not only a clinical imperative but a systems issue. Agencies must recognize the hidden biological toll of shift work and operational exposures.
- Scheduling Reforms: Minimize quick turnarounds and provide protected sleep opportunities.
- Nutrition Policies: Educate on the importance of bloodwork and vitamin and mineral deficiencies, provide nutrition education, and provide electrolyte replacement strategies during heat operations.
- Exposure Controls: Monitor PFAS in gear, enforce CO monitoring, and provide neurocognitive follow-ups after significant exposures.
- Screening Protocols: Annual endocrine, sleep, and autonomic assessments for shift-work personnel.
- Integrated Wellness: Combine peer support and mental health services with occupational and physiological screening.
By viewing firefighter wellness as encompassing both mind and body, agencies can lower misdiagnosis rates, enhance treatment effectiveness, and boost personnel’s quality of life, paving the way for long, healthy careers.
This article originally appeared within the Winter 2026 issue. Download the full issue here, or browse all back issues in theCRACKYL Library.
