Can hypothyroidism be mistaken for depression?

Yes. Fatigue, weight gain, forgetfulness, and low mood occur in both. NIDDK and MedlinePlus list depression among the symptoms of hypothyroidism. A TSH blood test separates the two.

Will levothyroxine help my depression if my TSH is only slightly high?

The trial evidence says probably not in older adults. In the TRUST trial of 737 adults aged 65 and older with subclinical hypothyroidism, levothyroxine did not improve symptom or tiredness scores. An ancillary study of 427 participants found no difference in depressive symptoms after 12 months.

How often should thyroid levels be checked on lithium?

The FDA label for lithium tells doctors to check thyroid function before treatment, at three months, and every six to twelve months during treatment. It says to check more often if results cause concern.

Is liothyronine (T3) approved by the FDA for depression?

No. The Cytomel label lists hypothyroidism and two other thyroid uses. Psychiatrists sometimes add T3 to an antidepressant off-label. In STAR*D, 24.7% of people reached remission with T3 and 15.9% with lithium, and the difference was not statistically significant.

Can a Thyroid Problem Cause Depression?

Q: Can an overactive thyroid cause depression too?

It more often causes nervousness, irritability, and trouble sleeping. NIDDK says hyperthyroidism in older adults is sometimes mistaken for depression or dementia. Older adults may lose appetite or withdraw from people.

The short answer: Yes, it can. Both NIDDK and MedlinePlus list depression as a symptom of an underactive thyroid (hypothyroidism). The link is smaller than doctors once thought. A 2021 meta-analysis in JAMA Psychiatry found an odds ratio of 1.30 for hypothyroidism and clinical depression. A blood test called TSH shows if your thyroid is part of the problem.

How can a thyroid problem look like depression?

The thyroid is a small gland in the front of your neck. MedlinePlus says its hormones affect nearly every organ and control functions that include heart rate, weight, digestion, and moods.

An underactive thyroid slows the body down. NIDDK lists these common symptoms of hypothyroidism:

Fatigue
Weight gain
Trouble tolerating cold
Joint and muscle pain
Dry skin or dry, thinning hair
Heavy or irregular periods
Slowed heart rate
Depression

The American Thyroid Association adds that you may feel sad or down and forget things easily. Several of these symptoms also occur in depression with a normal thyroid. Our guides to why depression makes you tired and the physical symptoms of depression cover that side.

An overactive thyroid speeds the body up. NIDDK lists nervousness, irritability, trouble sleeping, fatigue, a rapid heartbeat, and weight loss. Those symptoms look more like anxiety, and anxiety.md covers them. Older adults are different. NIDDK says hyperthyroidism in older adults is sometimes mistaken for depression or dementia. An older adult may lose appetite or withdraw from people.

How strong is the link between hypothyroidism and depression?

The link is real but modest. The 2021 JAMA Psychiatry meta-analysis pooled 25 studies with 348,014 participants. It counted only clinical depression, which means a formal diagnosis or a score above a set cutoff.

All hypothyroidism: odds ratio 1.30. An odds ratio of 1.00 means no link.
Overt hypothyroidism: odds ratio 1.77.
Subclinical hypothyroidism: odds ratio 1.13.
Women: odds ratio 1.48. The analysis did not confirm a link in men.

The authors wrote that the effect was considerably lower than previously assumed. They also wrote that the link was possibly restricted to overt hypothyroidism and to women.

Two terms matter here. In overt hypothyroidism, TSH is high and thyroid hormone is low. In subclinical hypothyroidism, TSH is high but the thyroid hormone thyroxine (T4) is still in the reference range. Subclinical hypothyroidism is the milder form, and its link to depression is weak.

Hypothyroidism is common. NIDDK says nearly 5 out of 100 Americans ages 12 and older have it, and most cases are mild. Many people will have both conditions by chance. A high TSH result does not prove that the thyroid caused the depression.

What does a TSH test show, and when should you get one?

TSH is thyroid-stimulating hormone. The pituitary gland makes it to tell the thyroid how much hormone to make. MedlinePlus explains that TSH rises when thyroid hormone is too low and falls when thyroid hormone is too high. One blood sample is enough.

The test has limits. MedlinePlus says a TSH test cannot show what is causing a thyroid problem. If the result is not normal, your doctor will probably order T4, T3, or thyroid antibody tests.

Guidance on who to test comes from the United Kingdom. The NICE thyroid disease guideline tells clinicians to consider thyroid tests for people with depression or unexplained anxiety. "Consider" is a weaker word than "offer" in NICE guidance. The guideline also warns that one symptom alone may not point to thyroid disease.

Ask your doctor about a TSH test if you have depression and any of these apply:

You also have cold intolerance, dry skin, hair thinning, constipation, or a slowed heart rate.
You have a risk factor that MedlinePlus lists: female sex, age over 60, a family history of thyroid disease, or a pregnancy in the past 6 months.
You take lithium.
Your depression did not improve with treatment.

thyroid.md explains thyroid conditions and their tests in more detail.

Does treating the thyroid lift your mood?

It depends on which form you have.

Overt hypothyroidism. Treatment is a medicine that replaces the missing hormone, usually levothyroxine. MedlinePlus says you get a blood test about 6 to 8 weeks after you start, and your doctor adjusts the dose if needed. Symptoms that come from low thyroid hormone are expected to ease as your levels return to range. Depression that has another cause will not ease, and it needs its own treatment.

Subclinical hypothyroidism. The evidence here is against a mood benefit. The TRUST trial gave levothyroxine or placebo to 737 adults aged 65 and older with subclinical hypothyroidism. After 1 year, hypothyroid symptom scores and tiredness scores did not differ between the groups.

A planned ancillary study of TRUST looked at depressive symptoms in 427 of those participants. The 12-month difference on a 15-point depression scale was 0.15 points, and the smallest difference that matters to patients is 2 points. The researchers also updated a meta-analysis and again found no meaningful effect. Most participants had few depressive symptoms at the start, so the study says little about people with a depression diagnosis.

The trial enrolled older adults only. For adults under 65 who have symptoms and a mildly raised TSH on two tests 3 months apart, the NICE guideline says clinicians can consider a 6-month trial of levothyroxine. It also says to consider stopping the medicine if symptoms persist after TSH returns to range.

Can lithium cause a thyroid problem?

Yes. Lithium treats bipolar disorder, and psychiatrists sometimes add it to an antidepressant. The FDA label for lithium says the drug concentrates in the thyroid and can block the production and release of thyroid hormone. That can lead to hypothyroidism. The American Thyroid Association also names lithium among medicines that can affect the thyroid.

A 2012 Lancet meta-analysis of 385 studies measured the size of the risk. Clinical hypothyroidism was more common in patients who took lithium than in those who took placebo, with an odds ratio of 5.78.

The label tells doctors to check thyroid function before treatment starts, at three months, and every six to twelve months after that. It says thyroid hormone treatment may be added if hypothyroidism occurs. Do not stop lithium by yourself. Tell your prescriber if your mood drops or you feel slow and cold while you take it.

Is thyroid hormone ever used to treat depression itself?

Sometimes, by psychiatrists, in people with a normal thyroid. The hormone is liothyronine, also called T3. It is added to an antidepressant when earlier treatments did not work. This is called augmentation.

The main evidence is from the STAR*D study. It randomly assigned 142 adults with major depression to add lithium or T3. All of them had two earlier medication steps that failed or that they could not tolerate. Remission rates were 24.7% with T3 and 15.9% with lithium, and the difference was not statistically significant. Fewer people left treatment because of side effects with T3: 9.6% compared with 23.2% with lithium. The authors called both remission rates modest.

This use is off-label. The FDA label for liothyronine (Cytomel) lists hypothyroidism and two other thyroid uses. It does not list depression. The label also warns about heart-related side effects in older adults and in people with heart disease. A psychiatrist makes this decision. Our guide to treatment-resistant depression covers the other options.

The bottom line

A thyroid problem can cause depression, and overt hypothyroidism has the clearest link. The link is modest, and it is weak for subclinical hypothyroidism. A TSH blood test is a reasonable step if you have depression with other thyroid symptoms, if you take lithium, or if treatment has not helped. Thyroid treatment helps when overt thyroid disease is the cause. Levothyroxine did not improve mood in older adults with subclinical hypothyroidism. If you have thoughts of suicide, call or text 988 in the United States.

Last updated: October 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor before you start, stop, or change any thyroid or psychiatric medicine.