But this didn’t explain why rates of depression have been steadily climbing. From 1991 to 2001, the rate more than doubled from 3.3 percent to 7 percent of adults; today, about 10 percent of Americans suffer from this disorder. Enter the inflammation theory: Inflammation occurs when you’re injured or exposed to disease-causing germs. In response, your body’s immune system releases chemicals called cytokines to fight off harmful organisms and repair damage. But now some experts believe that chronic exposure to cytokines—from inflammation caused by stress, diet, and environmental toxins—may lower serotonin and contribute to depression, says Charles Raison, MD, associate professor in the department of psychiatry at the University of Arizona.
Scientists first made the connection in the 1980s when they injected animals with bacteria to trigger inflammation. The animals exhibited symptoms of depression: lethargy, loss of appetite, and avoiding social contact. Subsequent studies by Dr. Raison and others have found that depressed people have higher levels of inflammatory chemicals such as C-reactive protein. Intrigued, Dr. Raison’s team gave infliximab—an anti-inflammatory drug that treats autoimmune diseases—to people with major depression and found that subjects with high levels of C-reactive protein reported greater improvement in depression symptoms than those without inflammation.
While inflammation isn’t likely the primary cause of depression, experts increasingly agree that it can prolong or worsen it. Treating depression in patients who have high levels of inflammation with anti-inflammatory drugs may have a big impact on their mood.
How You Can Use the News
The lifestyle choices that boost emotional well-being (healthy diet, exercise, sufficient sleep) also reduce the risk of inflammation—and thus depression. A Spanish study of more than 10,000 middle-aged adults showed that those who ate a diet high in processed foods were about twice as likely to develop depression compared with those who followed a Mediterranean diet (high in fish, fruits, vegetables, nuts, and monounsaturated fats such as those in olive oil). You may also lower inflammation risk by using meditation techniques, including deep breathing, walking meditation, or yoga. These activities help reduce stress-induced inflammation among people with an inflammatory-related disease such as rheumatoid arthritis or asthma, according to a 2013 study by researchers at the University of Wisconsin-Madison.
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