Physical causes of low mood: thyroid disease and vitamin B12 deficiency
Physical illnesses such as an underactive thyroid (hypothyroidism) or vitamin B12 deficiency (too little of the vitamin) can present like depression, so they are looked for before depression is diagnosed.
Remember
Thyroid disease, vitamin B12 deficiency, kidney disease and alcohol misuse are physical illnesses that can cause depression, so they should be looked for before depression is diagnosed.
Many physical illnesses can present like depression, so they are investigated and treated before a person is diagnosed with it. The recognised physical causes include thyroid dysfunction, vitamin B12 deficiency, kidney disease, and alcohol and drug misuse.
Thyroid dysfunction is a hormone disturbance. The thyroid is in the neck and its hormones set the body's metabolic rate, which is how quickly the body uses energy. With too little hormone (hypothyroidism, an underactive thyroid), the features include feeling cold more than usual, weight gain, constipation, tiredness, and low mood or depression. A blood test of thyroid function usually settles it, and the mood symptoms may improve once the thyroid problem is treated.
In the list of recognised physical causes, thyroid dysfunction is followed by vitamin B12 deficiency. Vitamin B12 is needed for healthy blood and nerves, and when it is lacking the NHS lists psychological problems that range from mild depression or anxiety to confusion and dementia. Numbness, pins and needles, and problems with balance and coordination can come along with them. A blood test for vitamin B12 can confirm it, and replacing the vitamin can improve both mood and nerve symptoms, although long-standing nerve damage may not fully recover.
The trap is to treat the mood alone and miss the underlying illness.
Key facts
- Physical causes
- thyroid dysfunction, vitamin B12 deficiency, kidney disease, and alcohol and drug misuse are physical illnesses that can present like depression.
- Underactive thyroid clues
- weight gain, constipation and feeling cold with low mood point to an underactive thyroid.
- Vitamin B12 clues
- low mood with numbness, pins and needles and balance problems points to vitamin B12 deficiency.
- First step for the thyroid
- check thyroid function with a blood test before settling on a diagnosis of depression.
- After treatment
- if the physical cause is found and treated, the mood symptoms may improve.
Exam traps
- Essential hypertension (high blood pressure with no other cause) is a common physical disease, but it usually causes no symptoms and is not a recognised cause of depression.
- Vitamin K deficiency is another vitamin deficiency, but it impairs blood clotting and causes a bleeding tendency, and it is not a recognised physical cause of depression.
- Vitamin B12 deficiency is a recognised cause of low mood, but with weight gain, constipation and feeling cold the features point more strongly to the thyroid.
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