Why does depression make you feel tired?

Depression can make you feel physically and mentally tired.

In fact, fatigue is one of the most common symptoms of major depressive disorder (MDD), showing up in around 90% of people with depression, according to some studies.

I was feeling so exhausted and sad at my worst that I simply couldn’t get out of bed a lot of days, never mind going to work.

How does depression cause tiredness?

1. Sleep disruptions

• • People with depression often experience insomnia, fragmented sleep, or hypersomnia (sleeping too much).

• • The sleep might not be restorative; even if you sleep a lot, your brain might not cycle through all the stages of deep sleep properly.

• • Disrupted sleep architecture affects energy, focus, and mood, leaving you wiped out.

A study confirmed a strong bidirectional link between depression and poor sleep quality, particularly insomnia.

My sleep was so disrupted that I would lie awake for hours during the night, mulling over negative thoughts and ruminating constantly. I would also wake up various times during the night, making me incapable of getting refreshing rest.

2. Neurochemical imbalances

• • Depression involves imbalances in neurotransmitters like serotonin, dopamine, and norepinephrine.

• • These chemicals are not just about mood since they also help regulate motivation, alertness, and physical energy.

• • Everything feels more effortful when they’re low, even “simple” things such as getting out of bed.

3. Inflammation and the immune system

• • Newer research shows that depression is often linked to chronic low-grade inflammation in the body.

• • Inflammatory cytokines (like IL-6, TNF-alpha) can disrupt brain function and create “sickness behavior”: fatigue, social withdrawal, low energy.

• • This response mimics how your body feels when you’re physically ill.

The term is called sickness behavior in the context of depression and inflammation.

4. Cognitive overload
   
   

• • Depression often comes with rumination, negative thoughts, and cognitive distortions.

• • Constant mental chatter drains your mental energy, much like how a computer runs slower with too many tabs open.

• • It leads to a sense of mental fatigue, poor concentration, and “brain fog.”

The constant rumination and adverse thoughts going on in my head exhausted me mentally and physically. This was most prevalent at night when I was alone with my thoughts without any distractions around.

5. Lack of motivation and pleasure (anhedonia)

• • It’s harder to generate the internal drive to act when nothing feels rewarding.

• • Tasks feel more exhausting since they require more conscious effort.

• • Over time, this can cause both physical exhaustion and emotional burnout.

6. Physical tension and motor slowing
   
   

• • Depression can cause psychomotor retardation, where you literally move and react more slowly.

• • Alternatively, some people experience restlessness or agitation, which also takes a toll.

• • Chronic stress and muscle tension, like a clenched jaw or tight shoulders, can add to physical fatigue too.

Unbeknownst to me at the time, I was a lot more tense and nervous than my usual self. I also caught myself slumping while walking more slowly.

7. Hormonal dysregulation

• • Depression is often linked to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which controls your stress hormone cortisol.

• • Cortisol concentrations in depressed people can be chronically elevated or erratic, causing the body to feel like it’s constantly in “fight-or-flight” mode.

• • This wears you down over time, causing adrenal fatigue-like symptoms: tired but wired, sluggish in the morning, and crashing in the afternoon.

Studies illustrated how HPA axis dysregulation contributes to mood and energy disturbances in depression.

8. Nutrient deficiencies
   
   

• • Depression can impact appetite, diet quality, and gut function, which can lead to or worsen deficiencies in:

• • • Iron (needed for oxygen transport and energy).

• • • Vitamin D (linked to both fatigue and low mood).

• • • B vitamins (especially B6, B12, and folate, which support energy metabolism and neurotransmitter synthesis).

• • • Magnesium and Omega-3s.

• • These deficiencies can independently add to mental and physical exhaustion.

Research noted that older adults with vitamin D deficiency were more likely to experience depression and fatigue.

9. Executive dysfunction

• • Depression impairs the brain’s executive functions, the mental skills you use to plan, start tasks, stay focused, and manage time.

• • You experience “decision fatigue” because every decision or task feels overbearing.

• • That constant mental gridlock leaves you drained, even if you haven’t physically done much.

I struggled to concentrate and had trouble processing information as quickly as I normally could. Thankfully, those cognitive problems dissolved once my mood improved.

10. Social exhaustion
    
    

• • Depression often causes or is worsened by social withdrawal, but even small social interactions can feel emotionally taxing.

• • Putting on a “normal face” for others can be incredibly tiring for those who mask how they feel.

• • The result is a burnout-like fatigue from just existing in social settings.

11. Chronic pain or somatic symptoms

• • Many people with depression also experience unexplained physical pain like headaches, muscle aches, or GI issues.

• • Living with continuous discomfort saps energy and adds to fatigue, even if you’re technically “resting”.

Studies have shown that up to two-thirds of people with depression report physical symptoms as a primary concern.

12. Emotional numbing
    
    

• • Emotional blunting or numbness can create a sense of disconnection from life, making everything feel flat, gray, and pointless.

• • This emotional deadness leads to a state of low arousal, where there’s no spark to engage with the world.

• • The result is a kind of existential tiredness that’s not easily explained but deeply felt.

While I felt extremely sad at first, it eventually evolved into numbness and apathy to the point where I felt “blank” all the time.

13. Unconscious energy drain from internal conflict

• • Depression often involves inner conflict. You might want to feel better, but also feel undeserving of it, or you know what would help, but can’t bring yourself to do it.

• • This constant internal tension quietly but consistently drains energy, like background apps on a phone eating up battery.

14. Reduced cardiovascular fitness from inactivity

• • Depression often leads to sedentary behavior during longer episodes.

• • This eventually causes deconditioning: your muscles weaken, your cardiovascular endurance drops, and your body uses more energy for simple tasks like climbing stairs.

• • The result is a fatigue feedback loop: you’re tired → you rest → you get less fit → you get more tired.

15. Negative interpretation bias
    
    

• • People with depression are more likely to interpret neutral or mildly challenging events as overwhelming or threatening.

• • This increases perceived effort by making regular tasks feel disproportionately exhausting.

• • It’s a subtle but powerful cognitive distortion that adds to subjective fatigue, even when energy output seems low on paper.

While I’ve always been a critical and perfectionistic person, I used to catastrophize and look at the negative side a lot more when I was severely depressed.

16. Autonomic nervous system (ANS) imbalance

• • Depression can alter autonomic regulation by shifting the balance away from parasympathetic (rest/digest) dominance toward chronic sympathetic (fight/flight) activation.

• • This dysregulation affects heart rate variability, blood pressure, and digestion, all of which influence energy levels.

• • You end up with poor physiological recovery even when at rest.

Research into HRV (heart rate variability) shows lower HRV in people with depression, reflecting poor recovery capacity and increased fatigue.

17. Overcompensation and “high functioning” exhaustion

• • Some people with depression push themselves to keep up appearances at work, in social life, or with family.

• • This constant masking or overcompensation often goes unnoticed until it crashes by burning through all emotional and physical energy reserves.

• • It’s like driving with one foot on the gas and the other on the brake.

18. Emotional suppression and avoidance
    
    

• • Depression can make people suppress emotions like sadness, anger, or vulnerability because they fear breaking down or being a burden.

• • Emotional suppression requires substantial mental energy to maintain.

• • This kind of chronic inner “bracing” leads to emotional fatigue, tension, and burnout.

19. Unresolved trauma or past stressors

• • Depression is entangled with past trauma, loss, or chronic stress for some, which can resurface or degrade during episodes.

• • This leads to a subtle but ongoing energy drain if the brain is constantly working in the background to manage unprocessed emotional content.

• • This is very true in people with complex PTSD or developmental trauma overlapping with depression.

20. Guilt and self-criticism
    
    

• • Depression often fuels harsh inner dialogue: “I should be doing more,” “I’m lazy,” or “I’m useless.”

• • This ongoing self-attack is mentally exhausting, like living with an inner bully who never lets up.

• • It drains willpower and stamina by adding emotional weight to every action.

Excessive self-criticism is linked to increased psychological distress and lower resilience.

I felt weak, like a burden, and like I had no reason to complain since there were many people out there who had it worse than I. I felt guilty because I was not functioning optimally and not living up to my potential.

It’s a vicious cycle

• Fatigue → less activity → more isolation → worse depression → more fatigue.

This cycle can be hard to break without support or treatment since the symptoms cause depression to persist and vice versa.

It’s multi-layered and self-reinforcing since all these factors often interact.

In summary

You can still feel bone-deep fatigue from the invisible load depression puts on your brain, body, and nervous system, even if you:

• Sleep enough.

• Aren’t in physical pain.

• Aren’t overly anxious.

Final thoughts

Depression can make you feel exhausted in ways that sleep alone can’t fix.

This isn’t laziness, weakness, or a lack of willpower; it’s a neurobiological and psychological condition that affects energy systems in the brain and body.

If you’re dealing with this kind of fatigue, you’re not imagining it. It’s real.

The good news is that it’s treatable with therapy (like CBT), medication, lifestyle changes (like regular movement or sleep hygiene), or a mix of all the above.

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