There was an article in the NYTimes discussing some recent studies which show a link between allergies and depression. Because an increase in suicide rates occurs in the Spring, the thought it that the manifestation of allergies, not just the genetics, can exacerbate depression.
This correlation is part of the teachings of Chinese Medicine, of course. The lung is the organ that protects the body. As well as its own functions, the lung rules over the skin the major barrier of the body and the nose. Not only is the emotion that is associated with the lung sadness, but also the lung is responsible for shielding the spirit from negative emotions and hostile energies. So it only stands to reason that people with allergies (low lung energy) would also be more susceptible to depression from a Chinese Medicine standpoint.
To read more about allergies and acupuncture please click here.
Some of the article is excerpted here.

April 11, 2011
Allergies Can Increase the Risk of Depression
By ANAHAD O’CONNOR

THE FACTS

Spring always brings a rash of sneezing, sniffling and stuffy noses. But can seasonal allergies be psychologically harmful?

A wave of emerging research suggests that may be the case. While there’s no firm evidence that allergies cause depression, large studies show that allergy sufferers do seem to be at higher risk of depression.

Severe allergies can bring sleeplessness, headaches, fatigue and a general feeling of physical depletion, all of which can worsen mood. Studies have found that allergic reactions release compounds in the body called cytokines, which play a role in inflammation and may reduce levels of the hormone serotonin, which helps maintain feelings of well-being. And it’s well known that some common allergy medications, like corticosteroids, can cause anxiety and mood swings.

Several large studies have found that the risk of depression in people with severe allergies is about twice that of those without allergies. In 2008, researchers at the University of Maryland reported that this link may help explain a widely established — but poorly understood — increase in suicides during the spring every year. Analyzing medical records, the authors found that in some patients, changes in allergy symptoms during low- and high-pollen seasons corresponded to changes in their depression and anxiety scores.

A Finnish population study in 2003 found a link between allergies and depression; however, women were much more likely to be affected. In 2000, a study of twins in Finland also showed a shared risk for depression and allergies, a result of genetic influences, the authors wrote.