Boing Boing contributor Cory Doctorow has a post about an article on the Discover website that talks about scientists who are trying to uncover the causes of schizophrenia:
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.”
A simple neurological exam showed Torrey that schizophrenics suffered from more than just mental disturbances. They often had trouble doing standard inebriation tests, like walking a straight line heel to toe. If Torrey simultaneously touched their face and hand while their eyes were closed, they often did not register being touched in two places. Schizophrenics also showed signs of inflammation in their infection-fighting white blood cells. “If you look at the blood of people with schizophrenia,” Torrey says, “there are too many odd-looking lymphocytes, the kind that you find in mononucleosis.” And when he performed CAT scans on pairs of identical twins with and without the disease—including Steven and David Elmore—he saw that schizophrenics’ brains had less tissue and larger fluid-filled ventricles.
Subsequent studies confirmed those oddities. Many schizophrenics show chronic inflammation and lose brain tissue over time, and these changes correlate with the severity of their symptoms. These things “convinced me that this is a brain disease,” Torrey says, “not a psychological problem.”By the 1980s he began working with Robert Yolken, an infectious-diseases specialist at Johns Hopkins University in Baltimore, to search for a pathogen that could account for these symptoms. The two researchers found that schizophrenics often carried antibodies for toxoplasma, a parasite spread by house cats; Epstein-Barr virus, which causes mononucleosis; and cytomegalovirus. These people had clearly been exposed to those infectious agents at some point, but Torrey and Yolken never found the pathogens themselves in the patients’ bodies. The infection always seemed to have happened years before.
Torrey wondered if the moment of infection might in fact have occurred during early childhood. If schizophrenia was sparked by a disease that was more common during winter and early spring, that could explain the birth-month effect. “The psychiatrists thought I was psychotic myself,” Torrey says. “Some of them still do.”
By the time Perron made his discovery, Torrey and Yolken had spent about 15 years looking for a pathogen that causes schizophrenia. They found lots of antibodies but never the bug itself. Then Håkan Karlsson, who was a postdoctoral fellow in Yolken’s lab, became interested in studies showing that retroviruses sometimes triggered psychosis in AIDS patients. The team wondered if other retroviruses might cause these symptoms in separate diseases such as schizophrenia. So they used an experiment, similar to Perron’s, that would detect any retrovirus (by finding sequences encoding reverse transcriptase enzyme)—even if it was one that had never been catalogued before. In 2001 they nabbed a possible culprit. It turned out to be HERV-W.
Several other studies have since found similar active elements of HERV-W in the blood or brain fluids of people with schizophrenia. One, published by Perron in 2008, found HERV-W in the blood of 49 percent of people with schizophrenia, compared with just 4 percent of healthy people. “The more HERV-W they had,” Perron says, “the more inflammation they had.” He now sees HERV-W as key to understanding many cases of both MS and schizophrenia. “I’ve been doubting for so many years,” he says. “I’m convinced now.”
Through this research, a rough account is emerging of how HERV-W could trigger diseases like schizophrenia, bipolar disorder, and MS. Although the body works hard to keep its ERVs under tight control, infections around the time of birth destabilize this tense standoff. Scribbled onto the marker board in Yolken’s office is a list of infections that are now known to awaken HERV-W—including herpes, toxoplasma, cytomegalovirus, and a dozen others. The HERV-W viruses that pour into the newborn’s blood and brain fluid during these infections contain proteins that may enrage the infant immune system. White blood cells vomit forth inflammatory molecules called cytokines, attracting more immune cells like riot police to a prison break. The scene turns toxic.
In one experiment, Perron isolated HERV-W virus from people with MS and injected it into mice. The mice became clumsy, then paralyzed, then died of brain hemorrhages. But if Perron depleted the mice of immune cells known as T cells, the animals survived their encounter with HERV-W. It was an extreme experiment, but to Perron it made an important point. Whether people develop MS or schizophrenia may depend on how their immune system responds to HERV-W, he says. In MS the immune system directly attacks and kills brain cells, causing paralysis. In schizophrenia it may be that inflammation damages neurons indirectly by overstimulating them. “The neuron is discharging neurotransmitters, being excited by these inflammatory signals,” Perron says. “This is when you develop hallucinations, delusions, paranoia, and hyper-suicidal tendencies.”
The first, pivotal infection by toxoplasmosis or influenza (and subsequent flaring up of HERV-W) might happen shortly before or after birth. That would explain the birth-month effect: Flu infections happen more often in winter. The initial infection could then set off a lifelong pattern in which later infections reawaken HERV-W, causing more inflammation and eventually symptoms. This process explains why schizophrenics gradually lose brain tissue. It explains why the disease waxes and wanes like a chronic infection. And it could explain why some schizophrenics suffer their first psychosis after a mysterious, monolike illness.