Anxiety can lead to feelings of excessive sleepiness or physical fatigue, a seemingly contradictory response to a state of high alert. This counterintuitive effect is common for many dealing with chronic worry. The body’s powerful stress response system is not built to sustain constant activation, and this sustained effort drains the body’s energy reserves.
The Paradox: Why Stress Causes Fatigue
The feeling of tiredness stemming directly from anxiety results from the body’s continuous engagement with the “fight or flight” response. This reaction, managed by the sympathetic nervous system, prepares the body for immediate physical action against a threat. Chronic anxiety causes the body to perceive a constant stream of non-physical threats, keeping this emergency system perpetually active.
This sustained high-alert state involves the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, the body’s central regulator of stress. When stimulated, the HPA axis triggers the release of stress hormones, notably cortisol and adrenaline. These hormones increase heart rate and muscle tension while diverting energy resources away from processes like digestion to fuel the perceived need for defense.
While a brief rush of adrenaline provides a burst of energy, the chronic release of these chemicals is taxing. Continuously mobilizing energy and maintaining hyperawareness requires significant metabolic expenditure, draining the body’s resources over time. The body eventually enters a state that mirrors the “exhaustion” stage of the general adaptation syndrome, where the energy required for constant vigilance becomes depleted.
The Vicious Cycle of Anxiety and Sleep Deprivation
Distinct from the direct energy drain of stress hormones, anxiety causes fatigue by severely disrupting nighttime sleep quality. The hyperarousal state associated with anxiety makes it difficult to transition into restorative sleep phases, even when physically exhausted. Racing thoughts, excessive worry, and physical tension keep the brain from winding down, often leading to insomnia symptoms like difficulty falling asleep or frequent awakenings.
Poor sleep quality prevents the body from spending enough time in the deepest stages, specifically non-rapid eye movement (NREM) deep sleep and rapid eye movement (REM) sleep, which are crucial for physical and cognitive restoration. The chronic lack of quality rest creates a significant sleep deficit that results in excessive daytime sleepiness (EDS).
This daytime fatigue, in turn, can heighten emotional reactivity and lower the threshold for stress, making the individual more prone to anxiety the next day. This creates a self-reinforcing pattern: anxiety causes poor sleep, leading to daytime fatigue and increased irritability. Worrying about the next night’s sleep serves as an additional trigger, making it even harder to fall asleep and cementing the vicious cycle.
When Daytime Sleepiness Requires Professional Attention
If fatigue and sleepiness extend beyond occasional grogginess and begin to cause chronic impairment, professional attention is warranted. Excessive daytime sleepiness is not a minor issue when it affects your ability to function safely at work, manage relationships, or perform daily tasks. Specific indicators that require consultation include a sudden onset of severe fatigue, feeling constantly tired even after a full night’s sleep, or experiencing cognitive impairment like brain fog or memory issues.
It is helpful to start by consulting a primary care physician to rule out other medical causes, such as thyroid issues, anemia, or underlying sleep disorders like sleep apnea. Your doctor can assess whether the symptoms suggest a co-occurring mental health issue, such as depression, which frequently presents alongside anxiety and fatigue. If symptoms are primarily related to sleep disruption, a referral to a sleep specialist may be appropriate for diagnostic testing.
For persistent anxiety and worry that interferes with your life, seeing a mental health professional, such as a therapist, is an important next step. Therapeutic approaches like Cognitive Behavioral Therapy (CBT) are highly effective in addressing both anxiety and insomnia, helping to break the negative feedback loop between worry and sleep disturbance. Seeking help early can prevent the symptoms from worsening.