Tiredness and depression – 10 root causes that help explain your fatigue

You are struggling with depression and are also just so unbelievably tired all the time. Here are 10 top root causes that help explain your battle with fatigue.
Tired and depression

I have yet to work with a client who is not struggling with fatigue alongside their depression. So if you are experiencing tiredness and depression then this post is for you. I delve into possible root causes of fatigue from a functional medicine perspective. 

A holistic perspective on tiredness and depression

I will try to keep the information simple because chances are high that you yourself are battling with fatigue. And that means your cognitive abilities might really be affected. 

In some cases, fatigue can be a symptom of a serious underlying condition such as cancer, kidney stones, multiple sclerosis or a chronic infectious disease. And if you are concerned, I’d encourage you to visit your doctor.

But in many cases, fatigue is not due to a life-threatening disease but rather other imbalances. So what are those?

Too much stress for too long (HPA dysfunction)

When we experience a lot of stress over a prolonged time without much of a chance to recover, then the stress response in our bodies can become exhausted. This can be from mental or physical stress. And let’s face it, in our modern-day culture that seems to celebrate being busy all the time, it’s not hard to become “burnt out”. 

You see, your nervous system and hormones respond to stress by secreting adrenaline and cortisol to help you deal with stressors. Those processes are beautifully orchestrated in your body via the HPA axis (the hypothalamic–pituitary–adrenal (HPA) axis). And normally, your body can respond quickly to stressful events and then also return just as rapidly to a normal state.  But this stress response and your HPA axis can become dysregulated when the stress has simply gone on for too long. And if you really haven’t had a break in a long time. 

Unfortunately, early life stress and trauma can impact on your HPA function and persist into adulthood if not addressed (1),(2).
So what this means is that significantly stressful experiences in your childhood can make you more sensitive to stress later on. Your nervous system may notice it more.

Signs of HPA dysfunction include:

  • not feeling refreshed upon waking
  • poor quality sleep including waking at night and being unable to fall back asleep easily
  • feeling tired all day but struggling to fall asleep at the end of day
  • decreased resilience to stress
  • brain fog or difficulty thinking straight
  • and of course having gone through a very stressful period lately.

Thyroid dysfunction

Your thyroid is a butterfly-shaped gland in your neck that regulates your metabolism (helping to turn food into energy). And a lot of people, women in particular, experience low thyroid function which means that the thyroid produces less of its hormones.

The effects of low thyroid hormone production include fatigue (the main symptom often), depression, dry skin, feeling cold all the time, difficulty losing weight, hair loss, constipation.

Interestingly, thyroid function is heavily influenced by stress. (A LOT of functions in your body are).

Blood sugar imbalances

Blood sugar imbalances are a topic I have covered quite a lot and I really encourage you to learn about it if you are struggling with fatigue. Listen to my podcast episode here to get started. 

Doctors often run tests in a patients complaining of persistent fatigue to see if you might be suffering from diabetes or pre-diabetes by checking your glucose and HbA1c markers. Why?

Your body gets its energy from glucose (sugar molecules) which come from the carbohydrates in your diet. And ideally, your glucose levels in your blood (your blood sugar levels) are nice and even throughout the day. But the way most of us eat in the Western World means that instead of nice even blood sugar curves, we get huge spikes and then troughs. And that can create a whole bunch of horrible feelings and symptoms – fatigue being a main one. 

I have just this week had someone over on Instagram message me to say how much his energy had improved by balancing his blood sugar levels for a month. He really couldn’t quite believe the drastic improvements. It can be very, very powerful.

Nutritional depletions

There are key nutrients needed for healthy energy production in the body and those include iron, the B vitamins, magnesium and zinc. Just to name a few. You also need to eat adequate and quality carbohydrates (think fibre), protein and fats. 

Your body simply needs the right fuel just as your car does, or it will eventually start to break down or certainly work less efficiently.

Poor digestion

You can eat the best diet in the world and yet, if your digestion isn’t working as well as it should, you might not be able to fully absorb the nutrients from your foods. And both your brain and body can feel those nutrient deficits as a result.

How do you know when your digestion and absorption might not be working efficiently? If you experience:

  • bloating
  • feeling very full very quickly after you start eating
  • lots of burping
  • lots of flatulence
  •  abdominal pain/cramps
  • nausea
  • constipation or diarrhoea (or indeed both)
To learn more about the link between your gut health and depression, head to this previous post

Celiac disease, food allergies, intolerances and sensitivities

In cases of persistent fatigue, your doctor might test you for celiac disease. It is an autoimmune disease whereby the body’s immune system attacks itself when gluten is eaten. It’s a serious condition which causes damage to the lining of the gut and that then means that your body can’t absorb nutrients properly. 

Food allergies, sensitivities and intolerances are different. 

Food allergies tend to be immediate reactions triggered by your immune system, e.g. tingling of the tongue and swelling of the lips every time you eat a certain fruit or nut. These reactions can be life-threatening for some with severe allergies.

A food sensitivity means that your immune system creates antibodies to proteins in foods that you’ve eaten and are sensitive to. To give an example, for some people that might be to gluten, dairy or eggs. These reactions aren’t life-threatening and the symptoms are often not immediate but can often include fatigue. 

A food intolerances, strictly speaking although this is often confused with food sensitivities, means that your digestive system struggles to break down certain parts of your food. A great example here is lactose intolerance. Lactose is a sugar in many dairy products and many people lack the enzyme lactase to break it down. And lactose intolerance has been associated with fatigue (3).

Food sensitivities and intolerances can be temporary so may not last forever. Improving your digestion and the health of your gut can be really helpful. 

I have had quite a few clients who have reported that they feel so much better, have more energy and can think more clearly if they avoid foods they are sensitive to. 


Disrupted sleep

This one is obviously a no-brainer. But it’s so important to highlight the importance of getting enough sleep if you are feeling tired. You can take supplements and try all sorts of energy boosting tips, but if you are simply going to bed too late and then not getting enough hours of sleep night after night, then it’s a good time to rethink your priorities. 

If you are struggling with sleep, take a look at my top 12 tips here.

Lingering infections

Sometimes the body might be struggling to get rid of an infection, such as Epstein Barr Virus which belongs to the herpes family. Long Covid is another example, where it’s possible that fragments of the virus can still remain with you even months after the initial infection (5). 

A sedentary lifestyle

Research has shown that not being very active physically is associated with higher levels of fatigue, and that meeting activity recommendations has benefits to your energy levels (4). 

Now I know it’s hard to move your body when you are experiencing tiredness and depression, but being active doesn’t have to mean hitting the gym or running for half an hour. Being active includes gardening, cleaning, going for walks, taking the stairs, dancing, stretching, swimming and so much more. 

Feeling stuck, lacking hope and not living an authentic life

And a another key contributor to fatigue in my professional opinion is this one:

Feeling like you are simply not living the way you truly want to live.

Perhaps you are feeling stuck and just can’t figure out a way to solve fundamental problems in your life. Maybe you are feeling controlled and are lacking a sense of freedom. And if you look at your life and what might lie ahead for you, perhaps you’re feeling disappointed and are lacking hope? Do you feel that you have to hide certain parts of yourself? That you can’t quite live an authentic life?

I do firmly believe that such beliefs can make you feel depressed and drag you out, and you end up feeling both physically and mentally very tired and drained.

Tiredness and depression - A way out

I hope it’s been useful to delve into the many possible reasons behind your fatigue. Tiredness and depression sadly go hand in hand, and often it really is a multitude of causes that all together make you feel so unwell. But it doesn’t have to stay that way. All of the root causes listed here offer a sense of hope that you can do something about them. 

If the root causes listed here make sense to you and if you feel ready to take action and make changes, why not get in touch with me to see if my work can help you feel fully alive and well again. Choose a time for a quick half hour Zoom chat by clicking on the button below. Zero obligation afterwards- let’s just chat!


1. Tomas, C., Newton, J., & Watson, S. (2013). A review of hypothalamic-pituitary-adrenal axis function in chronic fatigue syndrome. ISRN neuroscience, 2013, 784520. https://doi.org/10.1155/2013/784520

2 Ceruso A, Martínez-Cengotitabengoa M, Peters-Corbett A, Diaz-Gutierrez MJ, Martínez-Cengotitabengoa M. Alterations of the HPA Axis Observed in Patients with Major Depressive Disorder and Their Relation to Early Life Stress: A Systematic Review. Neuropsychobiology. 2020;79(6):417-427. doi: 10.1159/000506484. Epub 2020 Mar 23. PMID: 32203965.

3 Deng, Y., Misselwitz, B., Dai, N., & Fox, M. (2015). Lactose Intolerance in Adults: Biological Mechanism and Dietary Management. Nutrients, 7(9), 8020–8035. https://doi.org/10.3390/nu7095380

4 Ellingson LD, Kuffel AE, Vack NJ, Cook DB. Active and sedentary behaviors influence feelings of energy and fatigue in women. Med Sci Sports Exerc. 2014 Jan;46(1):192-200. doi: 10.1249/MSS.0b013e3182a036ab. PMID: 23783259.

5 Gaebler C, Wang Z, Lorenzi JCC, Muecksch F, Finkin S, Tokuyama M, Cho A, Jankovic M, Schaefer-Babajew D, Oliveira TY, Cipolla M, Viant C, Barnes CO, Bram Y, Breton G, Hägglöf T, Mendoza P, Hurley A, Turroja M, Gordon K, Millard KG, Ramos V, Schmidt F, Weisblum Y, Jha D, Tankelevich M, Martinez-Delgado G, Yee J, Patel R, Dizon J, Unson-O’Brien C, Shimeliovich I, Robbiani DF, Zhao Z, Gazumyan A, Schwartz RE, Hatziioannou T, Bjorkman PJ, Mehandru S, Bieniasz PD, Caskey M, Nussenzweig MC. Evolution of antibody immunity to SARS-CoV-2. Nature. 2021 Mar;591(7851):639-644. doi: 10.1038/s41586-021-03207-w. Epub 2021 Jan 18. PMID: 33461210; PMCID: PMC8221082.

tiredness and depression

Hello, I'm Claudia

I’m Claudia Smith, a qualified nutritional therapist, functional medicine practitioner and coach specialising in depression. This is where I share my thoughts and advice on natural and holistic approaches to overcoming depression.

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