Not only are there links to fatigue and metabolism, but researchers in Europe found that addressing this area may help stave off dementia-related disorders.
Depression rates among U.S. adults and adolescents have been climbing: these groups show a 60% increase in the mood disorder over the past decade, according to data from the CDC’s National Center for Health Statistics. Of course, depression can have many underlying and overlapping causes, spanning biological, psychological, and other factors—not to mention the social tensions of our time.
Now research has highlighted a possible medical issue that may be associated, suggesting that treating a particular organ could help manage mood. As part of their hypothesis for a June 2025 study, a group of biochemistry and physiology researchers from the Centre of Postgraduate Medical Education in Warsaw, Poland, stated: “Cognitive and mental illnesses are typically linked to clinical thyroid dysfunction.”
Their research, published in the journal European Thyroid Journal, suggested that autoimmune thyroid disease (AITD)—which they called “the most prevalent organ-related autoimmune condition”—is linked with an increased risk of mood disorders. “The growing body of evidence suggests that autoimmune thyroid disease can interfere with brain function,” they noted, with one meta-analysis of 20 previous studies suggesting “a strong association with psychiatric disorders such as depression and anxiety.”
Autoimmune thyroid disease—”encompassing Graves’ disease (typically linked with hyperthyroidism) and Hashimoto’s thyroiditis (generally associated with hypothyroidism)”—occurs when the immune system attacks proteins expressed by thyroid cells, which are involved in thyroid hormone synthesis. “Both hypo- and hyperthyroidism can substantially influence brain function, thereby affecting cognition and mood,” the team stated.
Hormones work like the body’s traffic lights, sending signals not only connected with metabolism and the reproductive system, but a multitude of physiological and chemical functions.
A January 2023 study, led by a group of India researchers and published in the journal Cureus, explained some of the possible mechanisms that could link changes in hormone levels to neuropsychiatric effects. Focusing on triiodothyronine (T3) and thyroxine (T4), two main hormones released by the thyroid which control the body’s metabolism, among other processes, they noted that there are a few ways that thyroid disorders could cause depression and other mood disorders, including by increasing inflammation and oxidative stress, triggering blood-brain barrier changes, and increasing the risk of diseases affecting the brain’s blood vessels. They added that “the presence of thyroid peroxidase antibodies is linked to depressive symptoms.” The Cleveland Clinic explains that thyroid peroxidase is an enzyme involved in thyroid hormone production.
The researchers also noted that besides producing feelings of “distress and sadness,” thyroid problems also increase risk of cognitive impairment, mania, psychosis, and more.
The Polish research team says that together, these takeaways underscore the importance of managing thyroid problems: “Given the association between hyperthyroidism and an increased risk of dementia, cognitive impairment and mood disorders, adequate treatment and careful monitoring of [autoimmune thyroid disease] patients are essential.”
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