There is no such thing as settled science. Ulcers, once thought to be caused by stress, have been discovered to be the result of an infection, no longer treated with a glass of milk and a less stressful job. Now, researchers are investigating depression along similar lines.

Depression is a serious problem, affecting 9.1% of American adults, according to a CDC study.  Anna North, writing in the New York Times, explains:

Turhan Canli, a professor of integrative neuroscience at Stony Brook University, …[is] looking at the possibility that depression could be caused by an infection.

“I’ve always been struck by the fact that the treatment options did not seem to have dramatically improved over the course of decades,” Dr. Canli told Op-Talk. “I always had a feeling that somehow we seem to be missing the actual treatment of the disease.”

He was intrigued by research showing a connection between depression and inflammation in the body, and he started to think about the known causes of inflammation — among them pathogens like bacteria, viruses and parasites.

In a paper published in the journal Biology of Mood and Anxiety Disorders, he lays out his case for rethinking depression as a response to infection. He notes that the symptoms of depression are similar to those of infection: “Patients experience loss of energy; they commonly have difficulty getting out of bed and lose interest in the world around them. Although our Western conceptualization puts affective symptoms front-and-center, non-Western patients who meet DSM criteria for major depression report primarily somatic symptoms.”

And, he writes, we already know that infectious agents can affect our emotions — he points to Toxoplasma gondii, a parasite that’s now somewhat famous (at least among science lovers) for its striking impact on its hosts. T. gondii can make rats like the scent of cat urine (causing obvious problems for the rats). In humans, it may have serious psychological effects — Dr. Canli cites research linking T. gondii with suicide. “Yet,” he writes, “large-scale studies of major depression and T. gondii or systematic searches to discover other potential parasitic infections have not yet been conducted.”

He believes researchers should compare tissue samples from depressed patients with those from non-depressed people, looking for evidence both of known pathogens and of new ones.

I have no idea if this hypothesis is correct, but it does demonstrate that those who claim global warming is settled science do not understand science.