A 41-year-old man came to us worn down in a way that had crept up on him over about six months. He was exhausted in a manner that sleep did not fix. His thinking had slowed, with a fog and heaviness that made ordinary mental work feel like wading through water. And his mood had sunk along with everything else. Put together, it looked like one of the most common conditions in medicine, and so that is what it was called. Depression.
He was started on an antidepressant, an SSRI, and given time for it to work. After three months something had shifted, but not enough. His mood had lifted partway. The fatigue, though, had not budged. He was still tired in his bones, still slowed, still not himself.
That partial response is the quiet centre of this whole case, because it is more treacherous than no response at all.
If you have been treated for depression and your mood improved a little but a deep physical fatigue simply will not lift, that gap is worth paying attention to rather than explaining away.
The symptoms he started with are the trouble, because they are gloriously non-specific. Exhaustion, mental slowing and low mood form a cluster that an enormous range of physical conditions can produce, not only depression:
- Persistent fatigue that rest does not repair, often the very first and most prominent complaint
- Cognitive slowing or brain fog, with poor concentration and a sense of mental heaviness
- Low or flat mood, which the body can produce from physical causes just as the mind can
- Aching joints, low libido and a general loss of drive, which often accompany the tiredness
- A gradual onset over months, building slowly rather than arriving with an obvious trigger
The problem is that this exact cluster is also the textbook face of depression. Without looking deeper, the two are almost impossible to tell apart from the outside.
What the first opinion concluded
His first assessment came from his GP and psychiatry, and it landed, reasonably enough, on a depressive episode. The plan was to continue the antidepressant and give it more time.
Depression is real, common and serious, and reaching for it when someone presents with low mood and fatigue is not a careless leap. It is often the right answer.
But there was a principle being skipped, and it is one doctors themselves describe. Depression is, in part, a diagnosis of exclusion. It is most safely made once the physical conditions that can masquerade as it have been ruled out. The catch is that this exclusion takes work, a proper look at the blood and the body, and it is tempting to treat the label as a conclusion that needs no further investigation. In his case the persistent, treatment-resistant fatigue was the disease still speaking, and the partial response to the SSRI had unfortunately served to half-confirm the wrong answer.
The second opinion
He was referred to internal medicine for a second opinion, and rather than adjusting the psychiatric treatment, they did something simpler. They ran a broader panel of blood tests.
The results rewrote the diagnosis:
- A strikingly elevated ferritin, the marker of the body's iron stores, far above the normal range (see the editorial note below regarding the exact value)
- A genetic test showing the HFE C282Y mutation in its homozygous form, the classic genetic signature of an inherited iron-overload disease
The diagnosis was hereditary haemochromatosis, one of the most common inherited conditions in people of Northern European descent, in which the body absorbs and stores far too much iron over the years. That excess iron gradually deposits in organs, and it is a recognised and often overlooked cause of exactly his symptoms: profound fatigue, low mood, cognitive slowing and joint pain. His depression had never been the disease. It had been a symptom of iron quietly poisoning his system.
Better still, the condition has a strikingly old and simple treatment. He was started on therapeutic phlebotomy, the controlled removal of blood at intervals, which forces the body to draw down its iron stores. As his ferritin fell back toward normal, his symptoms resolved completely. He reached full remission, and he no longer needed the antidepressant, because there had never been a primary depression to treat.
Why this case matters
The lesson lives inside the question this case asks.
Depression is a diagnosis of exclusion. The real question is whether we actually perform the exclusion, or whether it sometimes becomes the diagnosis that conveniently requires no further work.
A label that fits the symptoms is not the same as a label that has been earned by ruling out the alternatives. Fatigue with low mood has a long list of treatable physical causes, and several of them are found with cheap, routine bloodwork that takes minutes to order. The deeper trap in this case was the partial response. No improvement at all tends to make doctors rethink. A little improvement is more dangerous, because it offers just enough reassurance to keep everyone walking down the wrong road.
A word of balance
This is not a suggestion that depression is overdiagnosed as a rule, or that antidepressants should be doubted. Depression is genuinely common, the SSRI may well have helped his mood, and nobody should stop such medication on their own. The point is narrower and practical: when fatigue dominates the picture, when the response to treatment is incomplete, and when the basic medical workup has not been done, the physical possibilities deserve to be excluded properly before depression is accepted as the final word.
A second opinion is especially worth seeking when:
- Low mood is accompanied by heavy physical fatigue that does not improve even as the mood does
- You have been treated for depression with only a partial response, and the physical symptoms persist
- A broad set of blood tests has not been done to rule out physical causes of your fatigue
- Your instinct keeps telling you that something in your body, not only your mind, is wrong
Which leaves the question worth carrying into any consultation where a label is reached quickly: before tiredness and low mood are filed under depression, has anyone actually done the work of ruling out the body?
Note for readers: this is one case rather than medical advice by CW1. If this resonates with your situation, the right next step is a careful conversation with your own doctor, and not stopping any prescribed medication on your own.