I thought it was a mental health issue, but it was a physical illness—that can happen

“I haven’t been feeling like myself lately,” “I have no appetite and mornings are tough,” “I have absolutely no energy.”

Many people who experience this state for a long time feel anxious, wondering, “Could this be depression?”

But in fact, among those who come to psychiatric outpatient clinics thinking they might have depression, there are quite a few cases where the cause was actually a physical illness. I’d like to talk about that today.

Thyroid issues can look like depression

Have you ever heard of the thyroid? It is a small organ located in the front of the neck that releases hormones to regulate the body’s metabolism.

When the function of this thyroid drops, it causes fatigue, loss of energy, depression, memory loss, and weight gain—these are almost the same symptoms as depression.

I have actually experienced this in my outpatient clinic. A patient came in saying, “I haven’t had any energy for about three months,” and when we ran a blood test, it turned out to be hypothyroidism. After I referred them to the endocrinology department and they started treatment, they were completely back to their energetic selves a few months later.

Conversely, if the thyroid is overactive (as in Graves’ disease), it can cause palpitations, anxiety, irritability, and insomnia, which can sometimes be mistaken for panic disorder.

It can be detected through a blood test (TSH/FT4), so if you suspect something might be wrong, it is worth checking.

Sometimes the cause of “feeling generally unwell” is an iron deficiency

This is surprisingly common.

It is especially common in women, but iron-deficiency anemia can be the cause of fatigue, low mood, and difficulty concentrating.

What is interesting is that even if hemoglobin levels are within the normal range, some people experience symptoms just because their ferritin (stored iron) is low. There are cases where people were told they were “not anemic,” but when they checked their ferritin levels, they were found to be low.

Menopause—not just for women, but for men too

In women over 40, symptoms of menopause such as hot flashes, insomnia, depression, and irritability are very similar to depression, making them sometimes difficult to distinguish.

Although it is not widely known, men also experience “male menopause” (LOH syndrome). A gradual decline in the hormone testosterone can cause a loss of energy, depression, and difficulty concentrating. Instead of dismissing it as “maybe it’s just work stress” or “maybe it’s just my age,” checking your hormone levels can sometimes reveal the cause.

Cancer can also look like depression

This is a slightly frightening topic, but I am writing it down because it is important.

Medical literature has reported that in cases of pancreatic or lung cancer, depression or sudden drops in mood can appear even before a diagnosis is confirmed. It is believed that inflammatory substances released by the cancer affect brain function.

While we do not suspect cancer in everyone with depressive symptoms, if you also experience rapid weight loss, prolonged fever, night sweats, or pain in specific areas, a physical examination is necessary.

Even if 'tests show nothing,' if the symptoms are real

Even if tests find nothing, if your body feels consistently unwell—this is not 'all in your head.'

There is a condition known as 'somatic symptom disorder' (formerly somatoform disorder), which is understood as a problem with the brain's sensory processing. Psychiatric and psychosomatic approaches (such as cognitive behavioral therapy or medication) can be effective.

If you have been told 'everything is normal' everywhere you go but still feel unwell, please feel free to consult with us.

Psychiatry and psychosomatic medicine are places where we consider not only mental symptoms but also the underlying physical causes. Please feel free to consult us even at the stage where you think 'maybe it's depression' or 'I just don't feel quite right.'

We look forward to seeing you at City Light Clinic Mind and Body (Shinjuku).