Scientists are studying alternative explanations for complicated conditions like depression, and researchers from the University of Cambridge are looking into a preliminary but interesting theory that a protein released into our blood when our bodies are responding to infections—referred to as an inflammatory marker—may have a role in mental health.
The researchers hypothesize that there similar mechanisms that underlie chronic diseases, from heart disease and diabetes to mental illness and even skin diseases. In their new study published in the journal JAMA Psychiatry, they studied 4,500 people in long-term study called the Avon Longitudinal Study of Parents in Children. They looked at blood samples of the participants when they were 9 and checked in on the participants at 18 to see if they had depression or psychosis, or a history of it. The blood samples were assessed for levels of a protein called interleukin-6 (IL-6), an infection marker, and C-Reactive Protein, an inflammation marker.
Kids whose blood samples classified as having high levels of IL-6 were also shown to have double the likelihood of experiencing depression than people's whose IL-6 levels were low.
In a statement on their research, one of the study authors Dr. Golam Khandaker compared our immune systems to thermostats. Most of the time, thermostats are turned low and turned up high when we have an infection, but for some people, the thermostat is always turned up high. For these people, they may be more likely to have chronic syndromes, and be more likely to suffer depression.
Other research has looked at the link between inflammation and mental disorders. For instance, Gary Kaplan, an osteopath who runs the Kaplan Center for Integrative Medicine has argued that inflammation caused by hyperactivity of immune cells can impede blood flow to the brain and harm neural pathways. His argument is that there may be a link between inflammation and neural disorders like depression and dementia in the brain.
The research linking depression to inflammation and glitches in our immune systems is still very new, but it opens the possibly that treatments we already understand, like anti-inflammatory agents, could possibly be used, the authors say. While now it's still early science, it's a new way to look at a disease that's so complex—and can be hard to treat.