I have moderate to severe seasonal allergies. That means every year, when pollen counts climb, my sinuses are under siege. My eyes itch, my nose is stuffy. I pop allergy meds like candy. I’m lucky to make it out with only one sinus infection.

I am not alone in this. More than 50% of the population react to at least one type of seasonal allergen. It also turns out that on top of the misery this can cause, allergies and sinus problems may contribute to anxiety and mood changes.

Pollen counts are at their peak between May and July. In the south, it’s not uncommon for pollen counts to begin increasing as early as January. Typically, the longer springtime conditions last, the worse the pollen count remains. For those with seasonal allergies, high pollen counts mean higher allergy symptoms including headaches, itchy eyes, sneezing and a stuffy or runny nose.

Just coping with these symptoms is enough to cause symptoms of anxiety or depression, but there have been studies linking increased anxiety and depressive symptoms with increased levels of allergens, especially in those who are prone to more severe allergies. There is also evidence that a seasonal pattern of mania exists, with manic episodes peaking in early spring. There are a couple of reasons this could be the case.

The first is simple. Having congestion and a runny or stuffy nose can impede sleep. People with bipolar disorder are sensitive to changes in sleeping patterns. Lack of sleep can cause fatigue and problems with cognitive functions such as memory, decision-making and attention. Insufficient sleep can also increase the risk for suicide.

Another way allergies may be related to increased mood symptoms is part of the allergic reaction itself. Allergies are essentially the body treating pollen the same way it would treat a virus or infection. It sees generally harmless pollen as a threat and triggers an immune response.

Part of this response is to increase the level of cytokines in the body. Cytokines are small proteins that affect communication between cells, especially related to the immune system. Proinflammatory cytokines increase as part of immune response to infection, like what happens during allergic reactions and sinusitis.

Inflammation can affect the brain, and some people are especially sensitive to it. When this happens, serotonin and dopamine transmission is disrupted, which can cause mood symptoms. The inflammation can also impede function in areas of the brain including the prefrontal cortex, the anterior cingulate cortex, and the insula. Each of these control emotional response to some extent. The prefrontal cortex also controls cognitive function.

Unfortunately, while anti-inflammatory medications have shown some effectiveness at treating bipolar disorder, they are no match for medications specifically designed to treat symptoms of anxiety, mania and depression. Treating bipolar disorder and allergies separately will have to work for now.

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Image credit: Tina Franklin