What Is the Link Between Thyroid Imbalance and Depression?

The thyroid, a small gland located in the neck, plays an important role in a number of body functions. In some cases, a thyroid imbalance may contribute to depression as well as other types of mental health conditions.

Although it is estimated that around 12% of the U.S. population will develop a thyroid condition during their lifetime, the American Thyroid Association reports that 60% of people with a thyroid problem are unaware of their condition.

What Does the Thyroid Do?

As part of the body's endocrine system, the thyroid secretes hormones that help regulate energy levels and metabolism. Normally, the thyroid regulates various functions by releasing steady levels of thyroid hormones. 

Problems with this gland, however, can result in a thyroid imbalance that can affect the body in various ways. Thyroid imbalances can also contribute to mood problems such as depression and anxiety.

Types of Thyroid Imbalances

There are a number of different conditions that affect the thyroid, but two of the most common problems are hypothyroidism and hyperthyroidism.

  • Hypothyroidism, also known as an underactive thyroid, happens when the body does not produce enough thyroid hormones. It tends to affect women more frequently than men. It can occur at any age, but it also tends to be more common in adults over the age of 60.
  • Hyperthyroidism, also known as an overactive thyroid, happens when the body produces too much thyroid hormone. Many people who have an overactive thyroid experience some type of anxiety symptoms. However, research also suggests that depression is also very common, affecting as many as 69% of people with hyperthyroidism.

Other types of thyroid disorders and problems include Hashimoto's disease, Graves' disease, goiter, and thyroid nodules.

Symptoms of a Thyroid Imbalance

If you suspect you might have some type of thyroid condition, it is important to watch for symptoms. Talk to your doctor if you think that an underlying thyroid condition might be contributing to symptoms of depression, anxiety, or another mental health condition.

Symptoms of hypothyroidism include:

  • Constipation
  • Depression
  • Dry skin
  • Low libido
  • Tiredness
  • Sensitivity to cold
  • Sluggishness
  • Weight gain

Symptoms of hyperthyroidism include:

  • Anxiety
  • Diarrhea
  • Difficulty sleeping
  • Hair loss
  • Irritability
  • Muscle weakness
  • Nervousness
  • Rapid heart rate
  • Weight loss

The Thyroid and Depression

Researchers have long recognized that there is a link between thyroid function and depression, although the exact mechanisms of how they interact are not fully understood. Not only are people with thyroid disorders more likely to develop depression, but evidence also suggests that taking thyroid hormone treatments can enhance the effectiveness of antidepressants.

The metabolism of the thyroid hormones in the brain is a complex process that often involves many steps and pathways. If any of these components become impaired, it may have an impact on the thyroid's ability to signal the brain. 

Studies suggest that TSH levels are correlated to the severity of depressive symptoms. TSH, or thyroid-stimulating hormone, is a hormone secreted by the pituitary gland that acts to stimulate the production of more thyroid hormone.

Mild Hypothyroidism May Contribute to Depression

While more severe hypothyroidism might lead to more depressive symptoms, even cases of a milder underactive thyroid may cause problems. Some research has found that subclinical hypothyroidism, in which TSH levels are on the higher end of the normal range or barely above normal, may be linked to depression.

One study found that 63.5% of participants who had subclinical thyroid problems, or had symptoms of underactive thyroid but were below the diagnostic criteria for hypothyroidism, exhibited symptoms of depression. Treatment with thyroid hormone led to some relief, but it was not enough on its own to induce full recovery.

The connection between underactive thyroid and depression is strong enough that the American Association of Clinical Endocrinologists suggests that all people diagnosed with depression should be evaluated for subclinical or clinical hypothyroidism.

Depression, Hypothyroidism, or Both

One problem that can complicate diagnosis is that depression and hypothyroidism share some of the same symptoms. Low mood, fatigue, difficulty concentrating, decreased libido, and weight gain are common symptoms of both. 

In such cases, it can be helpful to look at some of the other symptoms that may indicate the presence of underactive thyroid. If your depressive symptoms are accompanied by constipation, dry hair and skill, hair loss, hoarseness, stiff muscles, and always feeling cold, it is more likely that your depression is related to hypothyroidism.

Getting Help

If you are experiencing symptoms of a thyroid imbalance, depression or both, it is important to talk to your doctor. Both conditions are treatable, and the sooner you start getting help the sooner you'll start feeling better.

Thyroid problems can often be diagnosed with a simple blood test. Once diagnosed, your doctor will prescribe medication to treat your condition. These thyroid medications can either reduce the body's production of thyroid hormones or replace the missing hormones to help improve both thyroid functioning and mood. 

Your doctor will also want to conduct blood tests periodically to see how effectively your medication is treating your thyroid problem and to make any needed adjustments in the type or dose of the medication you are taking.

Thyroid medications are sometimes combined with antidepressants to treat depression in people with normal thyroid functioning. In one older study, 23% of people who took T3 thyroid hormone along with their antidepressant treatment experienced improvements in their depressive symptoms.

More recent analysis has suggested that while combining thyroid medications with antidepressants is likely safe and effective, the complex relationship between depression and hypothyroidism requires further study.

For some people, treating the underlying thyroid imbalance can relieve depression. If you continue to experience symptoms of depression, your doctor may recommend the use of additional treatments such as antidepressants, psychotherapy, or a combination of the two.

A Word From Verywell

If you are experiencing symptoms of a thyroid imbalance, including symptoms of depression, be sure to discuss it with your doctor. Both depression and thyroid problems can be treated, the key is getting the right diagnosis. Most people with thyroid problems experience positive benefits from taking thyroid medication and feel that their depressive symptoms gradually resolve with time. 

If you or a loved one are struggling with depression, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kendra Cherry, MSEd
Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."