Sleepiness, Fatigue, or Depression? Mental Health Awareness Month Part 2

May is Mental Health Awareness Month! Project Sleep believes that mental health and sleep health are closely intertwined. We are excited to share interesting connections between sleep and mental health.

“Why am I always so tired?” 

When your energy feels off, it can be hard to know what’s wrong and what to do about it.  Feeling sluggish could be a sign of many things including anemia, thyroid issues, a sleep disorder, diabetes, depression, nutritional deficiencies, and so on. You may also wonder, “Will this go away or should I talk to a doctor about it?”

In everyday life, we use various terms interchangeably – feeling tired, exhausted, sleepy, fatigued, sluggish, weighed down, foggy, burnt out, like a zombie, or low-energy. But these terms may have different meanings. 

For example, at Project Sleep, we often hear from people with sleep disorders who faced excessive sleepiness for many years before finding an accurate diagnosis of sleep apnea, narcolepsy, or idiopathic hypersomnia. Even when an individual mentions sleepiness to a healthcare provider, it may be easily confused for depression or fatigue. 

Sleepiness, fatigue, and depression can all be invisible, sneak into a person’s life, and be difficult to explain to loved ones or doctors. 

So what are the key differences between sleepiness, fatigue, and depression? In this post, we break down each to help educate about similarities and differences. Being able to communicate about these symptoms is important to help find an accurate diagnosis, treatment, and a community of people who understand. 

Key Definitions

  • Sleepiness is the desire to fall asleep (a.k.a. drowsiness).
  • Fatigue is a lack of both physical and emotional energy and motivation (a.k.a. tiredness, exhaustion, and low energy).
  • Depression involves persistent feelings of sadness, disappointment and hopelessness, along with other emotional, mental, and physical changes that interfere with daily activities.

Still not sure what you are experiencing? Keep reading for much more on each.


Sleepiness is the desire to fall asleep (a.k.a. drowsiness). Sleepiness can look like:

  • struggling to keep eyes open
  • low energy, heaviness in limbs
  • lapses in alertness
  • slower reaction time
  • difficulty making decisions
  • eyes tearing
  • ability to sleep when given the chance

Sleepiness can be caused by:

  • being awake for a long enough period of time
  • an underlying sleep disorder (narcolepsy, circadian rhythm disorders, etc)
  • lack of quality sleep
  • a medication side effect
  • drinking alcohol

Sleepiness is relieved by:

  • Sleep

It’s normal to feel sleepy every now and then or take a nap on occasion. However, having difficulty staying awake during the day, on a regular basis for at least 3 months is considered excessive daytime sleepiness (EDS). If you’re struggling with sleepiness, consult a board-certified sleep specialist to see if you might have a sleep disorder.


Fatigue is a lack of both physical and emotional energy and motivation (a.k.a. tiredness, exhaustion, and low energy). Fatigue can look like:

  • sluggishness and heavy limbs
  • weakness
  • difficulty with concentration or memory
  • struggling to start or complete tasks
  • inability to nap when given the chance (even though you want to)

Fatigue can be caused by:

  • physical and mental exertion
  • stress
  • depression
  • sleep disturbances
  • physical illness
  • medications
  • dehydration
  • poor nutrition
  • lack of physical activity
  • boredom

Fatigue is relieved by:

  • rest
  • activity reduction
  • relaxation activities (i.e. yoga, mindfulness)
  • hydration
  • eating nutritious food
  • regular exercise

Fatigue after mental or physical exertion is normal. Ongoing fatigue for 6+ months with no known cause, that’s not improved with sleep or rest, and that worsens with physical or mental activity may be chronic fatigue syndrome (CFS). If you’re experiencing long-term or severe fatigue, speak with your doctor to determine the root cause.

The key differentiating factor between sleepiness and fatigue is the ability to fall asleep during the day when feeling tired and given the chance.


Depression involves persistent feelings of sadness, disappointment and hopelessness, along with other emotional, mental, and physical changes that interfere with daily activities. Depression can look like:

  • a lack of interest and pleasure in daily activities
  • feelings of worthlessness, excessive guilt, or hopelessness
  • significant weight loss or gain
  • insomnia or excessive sleeping
  • lack of energy
  • inability to concentrate
  • physical problems like headache, stomachache, or sexual dysfunction
  • recurrent thoughts of death or suicide

Depression can be caused by:

  • a personal or family history of depression
  • major stressors or traumas
  • certain medications
  • specific illnesses

Depression is relieved by:

  • psychotherapy
  • medication
  • lifestyle management (regular exercise, quality sleep, a healthy diet, avoiding alcohol)

We all experience sadness every now and then, and that’s healthy. When feelings of sadness continue for 2+ weeks and are felt nearly all day, nearly every day, they may be clinical depression. If you are experiencing symptoms of depression, it’s important to seek help from your doctor or mental health professional.

Blurry Lines

Parsing out the difference between sleepiness, fatigue, and depression, or which came first, is often much easier said than done. They overlap and interact a lot. The feedback loop between sleep issues and depression can be tricky, but understanding the complex relationship can be crucial to better managing both.

There is no “one-size-fits-all” treatment for depression, sleepiness, or fatigue; we’re all different! Finding the right treatment for you may take some trial and error, but remember: help and support are available!

Written by Anna Marr

It’s normal for people to feel tired or overwhelmed sometimes. If mood changes and feelings of anxiety or unhappiness are severe, or if they last longer than 2 weeks, please consider seeking a medical professional.

If you or someone you know is struggling with mental health or suicidal thoughts, round-the-clock help is available through the National Suicide Prevention Lifeline at 1-800-273-8255, the Veterans Crisis Line and Military Crisis Line at 1-800-273-8255, and the Crisis Text Line by texting “hello” to 741741.

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