Thyroid problems can affect mood in both directions. An underactive thyroid (hypothyroidism) can bring fatigue, weight gain and depression. An overactive thyroid (hyperthyroidism) can bring nervousness, irritability, a racing heart and trouble sleeping, which can feel a lot like anxiety. The National Institute of Mental Health names thyroid disorders among the conditions that can cause the same symptoms as depression.
Part of our guide: A Guide to Integrative Psychiatry
The good news is that this is checkable with a blood test. The honest news is that symptoms like these often have other causes, and the research link between an underactive thyroid and depression is smaller than many people assume. Knowing both helps you ask for the right test without expecting it to explain everything.
How the symptoms overlap
The thyroid makes hormones that help set the pace of many body systems. When levels run low or high, the effects can look psychological. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists these common symptoms:
| Underactive thyroid | Overactive thyroid | |
|---|---|---|
| Mood, energy and sleep | Depression, fatigue | Nervousness, irritability, fatigue, trouble sleeping |
| Heart | Slowed heart rate | Rapid or irregular heartbeat |
| Weight | Weight gain | Weight loss despite increased appetite |
| Temperature | Trouble tolerating cold | Sweating or trouble tolerating heat |
| Other clues | Joint and muscle pain, dry skin or thinning hair, heavy or irregular periods | Shaky hands, muscle weakness, frequent bowel movements, a goiter (neck enlargement) |
NIDDK's lists are on its hypothyroidism and hyperthyroidism pages. It also says these symptoms vary from person to person, and that many of them, especially fatigue and weight gain, are common and do not necessarily mean a thyroid problem. Hypothyroidism develops slowly, so changes can go unnoticed for months or even years. That slow onset is one reason people may read it as a gradual slide into depression.
Age can change the picture too. NIDDK notes that in older adults, hyperthyroidism is sometimes mistaken for depression or dementia, with symptoms such as loss of appetite or withdrawal from others instead of the classic jittery presentation. So an overactive thyroid does not always look anxious.
What the research says about mood
The evidence supports a real link, with a modest size. A 2021 meta-analysis of 25 studies and more than 348,000 people found that hypothyroidism and clinical depression were associated, with an effect "considerably lower than previously assumed." The association was stronger with full (overt) hypothyroidism than with the milder subclinical form, and the authors said it may be largely limited to overt disease and to women.
An earlier meta-analysis of case-control studies looked at autoimmune thyroiditis, including Hashimoto's disease, and reported higher odds of depression and anxiety disorders. Those studies varied widely and the depression results showed signs of possible publication bias. The 2021 review found the link with thyroid autoimmunity alone to be inconclusive. Put together, the evidence does not establish that thyroid antibodies on their own explain mood symptoms.
These studies show association, which is different from proof that one causes the other. Both depression and thyroid disease are common, so many people will have both by chance. Someone can also have a thyroid condition and a separate depressive or anxiety disorder that needs its own care.
How thyroid problems are checked
NIDDK says a diagnosis can't be based on symptoms alone. The usual path is:
- TSH first. TSH is a pituitary hormone that tells the thyroid how much hormone to make. Clinicians usually check it first. A high TSH most often points to an underactive thyroid, and a low TSH usually points to an overactive one.
- T4, and sometimes T3. If TSH is abnormal, at least one more test follows. Many clinicians prefer free T4. T3 helps when hyperthyroidism is suspected but T4 is normal.
- Antibodies, when indicated. These can help identify autoimmune causes such as Graves' disease and Hashimoto's disease, usually after other results suggest thyroid disease.
A few things can affect how results read. Pregnancy and birth control pills can raise thyroid hormone levels, and severe illness and corticosteroids can lower T4. The FDA also warns that biotin, often found in supplements, can significantly interfere with certain lab tests. The American Thyroid Association says biotin can make several thyroid tests look abnormal when they are actually normal, and that it should not be taken for 2 days before the blood draw. Tell the ordering clinician everything you take, and follow their directions about whether to pause anything.
The U.S. Preventive Services Task Force found the evidence insufficient to assess screening in nonpregnant adults without symptoms. That finding is about screening people who feel well. Someone with new depression, anxiety or fatigue is in a different position, and asking whether a thyroid test makes sense is a reasonable question. The Task Force also reports that the American Thyroid Association and the American Association of Clinical Endocrinologists recommend considering screening for hypothyroidism in people older than 60 and active case finding in people at higher risk. A broader overview is in which lab tests are used in integrative psychiatry.
Who may want to ask sooner
According to NIDDK, the following can raise the odds of thyroid disease:
- Being a woman, or being over 60
- A past thyroid problem, or thyroid disease in the family
- Type 1 or type 2 diabetes, celiac disease or lupus (for hypothyroidism)
- Nicotine use, high iodine intake or a recent pregnancy (for hyperthyroidism)
- Taking lithium or certain heart or cancer medicines that can interfere with thyroid hormone
After having a baby
Postpartum thyroiditis affects about 1 in 20 women within the first year after delivery, according to NIDDK. The American Thyroid Association gives a higher range, approximately 5-10% of women in the United States. It can start with an overactive phase, with symptoms such as irritability and trouble sleeping, followed by an underactive phase. NIDDK notes that underactive symptoms may be mistaken for the "baby blues." Not everyone goes through both phases. Anyone with new mood symptoms after birth should speak with a doctor promptly, since postpartum depression and thyroid problems can both occur. See our postpartum and perinatal mental health page for more.
If you take lithium
NIDDK lists bipolar disorder medicines among those that can interfere with thyroid hormone production. The lithium label says to monitor thyroid function before starting, at three months and every six to twelve months. If you take lithium and feel more depressed or slowed down, tell your prescriber so thyroid function can be part of the conversation. Please do not change the dose on your own.
The gray zone: subclinical hypothyroidism
Subclinical hypothyroidism means TSH is elevated while free T4 is normal. People with this result and low mood often want to know whether thyroid medicine would help. The evidence is more discouraging than many expect:
- A meta-analysis of 21 randomized trials found thyroid hormone therapy was not associated with improvements in quality of life or thyroid-related symptoms.
- In a trial of 427 adults aged 65 or older, depressive symptoms did not differ between levothyroxine and placebo after 12 months. Average depression scores were very low at the start, which limits what it says about people who are depressed now.
- A BMJ guideline panel made a strong recommendation against thyroid hormones for most adults with this result. It does not apply to women trying to become pregnant or people with TSH above 20 mIU/L, and it may not apply to people with severe symptoms or young adults.
- Not every guideline goes that far. The same BMJ paper says guidelines have tended to recommend treatment for TSH above 10 mIU/L, and for some people with lower values who are young, symptomatic or have specific indications. The 2012 guideline from the American Association of Clinical Endocrinologists and the American Thyroid Association says the decision to treat when TSH is below 10 should be tailored to the person.
Treatment decisions here belong with your doctor, and some people fall into those exceptions. For most others, a mildly high TSH is unlikely to be the whole explanation for persistent depression, so the mood symptoms deserve their own evaluation.
If a thyroid problem is found
Hypothyroidism is treated by replacing the hormones your thyroid can no longer make, usually with levothyroxine, with blood tests about 6 to 8 weeks after starting. Hyperthyroidism is usually treated with medicines, radioiodine therapy or surgery. Beta-blockers can ease symptoms such as tremor and rapid heartbeat, though they do not stop hormone production. An endocrinologist or primary care doctor usually manages this.
Mood may improve as thyroid levels settle, but that is not guaranteed. If depression or anxiety continues once levels are in range, it does not mean you are imagining it. It may be a separate condition that responds to its own treatment. See depression treatment and anxiety treatment. Keeping your thyroid doctor and mental health clinician in contact helps, so each knows what the other is changing.
Preparing for the conversation
- Write down when symptoms began and any physical changes, such as weight, temperature tolerance or heart rate.
- Bring past thyroid results if you have them.
- List every medication and supplement.
- Mention pregnancy, recent childbirth or a family history of thyroid disease.
For how this fits into a whole-person assessment, read about integrative psychiatry at Mind Body Seven or the article on what to expect at a first integrative evaluation. Which tests a clinician may order is something to ask the intake team.
FAQs
Can an antidepressant fix mood symptoms caused by the thyroid?
An antidepressant does not treat the thyroid problem itself. If thyroid disease is found, it needs its own treatment. Whether a person also needs depression treatment is a decision for their clinicians.
My thyroid test was normal. Could it still be my thyroid?
A normal TSH makes a thyroid cause less likely. It has limits: the American Thyroid Association notes that if the pituitary is damaged, the test may not help. A clinician may look further if your symptoms or medical history point that way. Ask whether repeat testing or other tests make sense, and keep looking at other explanations too.
Do I need a psychiatrist or an endocrinologist?
Often both roles matter. A primary care doctor or endocrinologist usually manages the thyroid, and a psychiatrist evaluates and treats mood or anxiety. Our article on where to start can help you decide.
Should I take iodine or a thyroid support supplement?
Do not start one without talking with your doctor. High iodine intake is listed by NIDDK as a risk factor for hyperthyroidism, and supplements can interact with medications.
