No one knows for sure what causes RA, but new research concludes that a deficiency in serotonin may contribute to symptoms.

The term serotonin is often recognized when it’s used to discuss depression and mood disorders.

Serotonin helps regulate mood and many antidepressant and antianxiety drugs act in concert with this important neurotransmitter.

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Recent studies have shown a link between rheumatoid arthritis (RA) — an autoimmune disease with physical symptoms — and emotional or mood disorders as well as a link between RA and cognitive impairment.

Likewise, conditions such as depression and anxiety also have physical symptoms that include pain or discomfort.

Much like emotional disorders, autoimmune diseases are complex.

These multifaceted illnesses do not fit neatly into one box. The treatments also vary. They may include chemotherapy, acupuncture, immunotherapy, steroids, marijuana, bee venom, or antimalarial drugs.

Some rheumatologists also prescribe drugs such as Cymbalta or Lyrica — traditionally used to treat depression and anxiety — to manage pain in patients with rheumatic or chronic pain disorders such as RA, lupus, and fibromyalgia.

That’s where the potential link emerges between serotonin deficiency and RA.

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The latest study found that mice with RA that lacked the ability to synthesize serotonin faced an increase in RA disease symptoms and pathology.

Not only did their RA disease activity increase, but the mice missing an enzyme required to convert serotonin also faced more bone and cartilage destruction.

Researchers said the findings indicate there is a link between the lack of serotonin and arthritis.

The mouse model could be a good predictor when it comes to humans with RA, too.

The study “…could represent an exciting prospect to regulate the immune response in RA and open new perspectives to improve the therapeutic options for patients,” said co-lead investigator Marie-Christine de Vernejoul of the Hôpital Lariboisière, Unité Mixte de Recherche (UMR) 1132, Université Paris Diderot, in a statement to the press.

Serotonin is also often active in the constriction of smooth muscles, but it turns out that it may have a role in bone and joint health, too.

This discovery could be an important part of the framework needed to establish new treatments for patients suffering with RA.

If the link can be further investigated, individuals with serotonin deficiency can be targeted and screened for RA early on.

Drugs used to increase serotonin in the body may also be used to treat people living with RA if these findings are confirmed.

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