An early 20th-century schizophrenia patient used a pin or a fingernail to scratch this artwork into a hospital wall.

Schizophrenia has historically been blamed on everything from bad DNA to bad parenting (imagine the unfairness of that for a moment), but some in the scientific community are championing the idea that the illness stems from a virus that we all carry. An excerpt from a Discovery article about this theory:

“Schizophrenia is usually diagnosed between the ages of 15 and 25, but the person who becomes schizophrenic is sometimes recalled to have been different as a child or a toddler—more forgetful or shy or clumsy. Studies of family videos confirm this. Even more puzzling is the so-called birth-month effect: People born in winter or early spring are more likely than others to become schizophrenic later in life. It is a small increase, just 5 to 8 percent, but it is remarkably consistent, showing up in 250 studies. That same pattern is seen in people with bipolar disorder or multiple sclerosis.

‘The birth-month effect is one of the most clearly established facts about schizophrenia,’ says Fuller Torrey, director of the Stanley Medical Research Institute in Chevy Chase, Maryland. ‘It’s difficult to explain by genes, and it’s certainly difficult to explain by bad mothers.’

The facts of schizophrenia are so peculiar, in fact, that they have led Torrey and a growing number of other scientists to abandon the traditional explanations of the disease and embrace a startling alternative. Schizophrenia, they say, does not begin as a psychological disease. Schizophrenia begins with an infection.

The idea has sparked skepticism, but after decades of hunting, Torrey and his colleagues think they have finally found the infectious agent. You might call it an insanity virus. If Torrey is right, the culprit that triggers a lifetime of hallucinations—that tore apart the lives of writer Jack Kerouac, mathematician John Nash, and millions of others—is a virus that all of us carry in our bodies. ‘Some people laugh about the infection hypothesis,’ says Urs Meyer, a neuroimmunologist at the Swiss Federal Institute of Technology in Zurich. ‘But the impact that it has on researchers is much, much, much more than it was five years ago. And my prediction would be that it will gain even more impact in the future.'”