When people hear the word depression, they typically group it into the category mental disorder. However, a new study by researchers from the University of Granada suggests that due to oxidative stress, the problem should actually be considered a systemic disease.

As it stands, depression is classified as a serious medical illness with mood, cognitive, and physical symptoms that's associated with higher rates of chronic disease, increased health care utilization, and impaired functioning, according to the Centers for Disease Control and Prevention (CDC). 

Researchers are hopeful that their findings could potentially one day explain the associations depression has with cardiovascular diseases and cancer, as well as why people suffering from depression tend to die younger than others without the health problem.

Statistics from the Depression and Bipolar Support Alliance show that major depressive disorder affects almost 15 million Americans or about 7 percent of the U.S. population 18 and older, during any given year. While major depressive disorder can develop at any age, the median age at onset is 32 and the problem appears to be more common in women than men. 

People with depression are four times as likely to develop a heart attack than those without a history of the illness. After a heart attack, individuals with depression are also at a significantly increased risk of death or second heart attack, according to the National Institute of Mental Health, as well as many other health conditions.

During this recent study, researchers conducted a meta analysis of 29 studies comprised of nearly 4,000 people, focusing on the imbalance between the individual increase of various oxidative stress parameters, specifically malondialdehyde. Malondialdehyde is a biomarker that measures oxidative deterioration of the cell membrane and the decrease in antioxidant substances, including uric acid, the superoxide dismutase enzyme and zinc.

From this study, researchers proved that treatments for depression help in lowering malondialdehyde levels that are typically higher in depressed patients. When patients were on a depression medication regimen, their malondialdehyde levels were thus lowered to that of a healthy individual. At the same time, increasing zinc and uric acid levels to those seen in a healthy individual helped with treatment. 

The study is published today in the Journal of Clinical Psychiatry.