Physical fatigue from physical health conditions is easy to understand. A broken leg, a chest infection, or a chronic illness like cancer clearly demands energy from the body, leaving someone understandably worn out. But what about fatigue linked to mental health? It’s far less visible, yet just as real—and in some cases, even more debilitating.
Fatigue is one of the most commonly reported symptoms by people experiencing depression, anxiety, PTSD, and related conditions. This kind of fatigue doesn’t always make sense to the outside world. Someone might be sleeping all the time, or barely sleeping at all. They might appear rested, yet still feel completely drained. In occupational rehabilitation, understanding the physiological and psychological roots of this fatigue is critical—not just for empathy, but for effective intervention and recovery.
The Mental Overload: How Cognitive Fatigue Builds Up
One key contributor to mental health-related fatigue is cognitive load. People with anxiety, PTSD, and depression often spend their days in a state of hyper-awareness or mental overactivity—replaying conversations, worrying about the future, or trying to suppress intrusive thoughts. This constant cognitive strain can cause a drain similar to running a marathon: it taxes attention, memory, and executive function, and over time, the brain becomes exhausted. Research shows that people with depression exhibit increased default mode network (DMN) activity—a part of the brain that lights up during self-referential thought and rumination. A 2020 study by Kaiser et al. (1) found that this elevated DMN activity correlates with both depressive symptoms and mental fatigue. The brain is working overtime, and it’s tiring.
The Body in Survival Mode
Mental health conditions like PTSD and anxiety keep the body locked in a near-constant state of fight-or-flight. This chronic stress response floods the system with cortisol, adrenaline, and other stress chemicals that, over time, wear down the immune system, interfere with digestion, and drain physical energy. What was designed as a short-term survival mechanism becomes a daily background hum of physiological overdrive. In his landmark book The Body Keeps the Score, Dr. Bessel van der Kolk (2) explains how trauma “lives in the body”—contributing to muscle tension, sleep disturbance, and even changes in heart rate variability. This physical hyperarousal is not just emotionally taxing—it’s metabolically exhausting.
The Sleep Deprivation Loop: When Rest Isn’t Restorative
Sleep and fatigue are deeply intertwined. Mental health conditions regularly disrupt sleep quality and quantity—resulting in a state where people may be in bed for hours but never truly feel rested. Whether it’s anxiety causing fragmented sleep, or depression leading to hypersomnia (excessive sleep), the body is missing out on deep, restorative sleep that’s critical for cellular repair and cognitive function. According to the Sleep Foundation (3), up to 80% of people with depression report significant sleep disturbances. Without this foundational reset, each day begins with a physiological disadvantage— a daily compounding of fatigue that feels impossible to shake.
When Movement Stops, Energy Declines
Depression and trauma often reduce motivation and activity levels. This may look like laziness from the outside, but inside, it’s a neurochemical response that slows both movement and thought—known as psychomotor retardation (4). The less someone moves, the more their capacity to generate energy declines. This isn’t just about fitness; regular movement supports mitochondrial function (the tiny energy producers in our cells), improves mood-regulating neurotransmitters like serotonin and dopamine, and helps break the cycle of fatigue and deconditioning. Inactivity begets more inactivity, but the right kind of movement—safe, supported, and paced—can help reverse that downward spiral.
Exercise Physiology in Action
Movement, when tailored appropriately to someone’s energy levels and symptoms, can begin to rewire the brain, reset the nervous system, and rebuild physical and cognitive stamina. Our Bounce program is our well-established approach to managing fatigue in all its forms, including from ME / CFS, long COVID, cancer recovery, mental health, and beyond (check out our recent blog on this!). It focuses on regulating the nervous system, pacing energy levels, and gradually restoring function through strategic movement. Headstrong is our new mental health program, specifically designed for individuals navigating anxiety, depression, or PTSD.
Bounce vs Headstrong?
You might be wondering, which program is best when fatigue is the main barrier: Bounce or Headstrong? While both programs use biotechnology and a nervous system lens—prioritising pacing and incremental progress—the difference lies in their emphasis. Headstrong includes fatigue as part of a broader picture, incorporating strategies like behavioural activation and structured support to improve mood, motivation, and self-efficacy alongside physical recovery.
Ultimately, both programs help clients break the fatigue cycle, but the right fit depends on whether fatigue is the primary issue—or a symptom of a deeper mental health challenge. You can compare our range of programs here!
Fatigue in mental health is complex, but it’s not untouchable. With the right lens, the right program, and the right kind of support, we can help clients reclaim their energy—and their lives.
Reach out if you have a client who would benefit from exercise physiology support.
References:
- Kaiser, R. H., Andrews-Hanna, J. R., Wager, T. D., & Pizzagalli, D. A. (2015). Large-scale network dysfunction in major depressive disorder: A meta-analysis of resting-state functional connectivity. JAMA Psychiatry, 72(6), 603–611. https://doi.org/10.1001/jamapsychiatry.2015.0071
- Bessel van der Kolk. The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. 2014.
- Sleep Foundation. (n.d.). Depression and Sleep. Retrieved from https://www.sleepfoundation.org/mental-health/depression-and-sleep
- Sandmeir A, Schoenherr D, Altmann U, Nikendei C, Schauenburg H, Dinger U. Depression Severity Is Related to Less Gross Body Movement: A Motion Energy Analysis. Psychopathology. 2021;54(2):106-112. doi: 10.1159/000512959. Epub 2021 Mar 1. PMID: 33647901.
Author: Yolanda van Vugt
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