Study of twins hints a virus may be partly involved in schizophrenia

Dr. E. Fuller Torrey is known in the field of psychiatry as th doctor who has spent a lengthy career searching for and talking about the likelihood that a virus could cause schizophrenia.

Not one of the dozens of microscopic bugs studied seemed to fit into the puzzle of mental illness. But now, after 20 years, the Washington-based researcher may have hit pay dirt with an organism that has never been described in humans but, for reasons yet unexplained, has shown up in about half the schizophrenics he studied.


"I have always maintained that if we could explain 10 percent of the cases of schizophrenia, I would be perfectly happy," Dr. Torrey said. "We are excited by the finding. We are not looking for a single cause for the disease."

The new evidence, based on studies conducted on identical twins, one healthy and one with schizophrenia, supports the argument that a virus can lie dormant in the brain and wreak havoc on areas that govern mood, thought and language.


Schizophrenia, a condition that has people hearing voices, believing delusions and losing touch with reality, occurs in 1 percent of the population but is found in a higher percentage within affected families. The illness can strike in the prime of life, the late teens or early 20s, causing thought and memory problems, hallucinations, inappropriate emotions and apathy.

Newer studies by Dr. Torrey and Barbara Fish of the University of California, Los Angeles, have found striking evidence that neurological differences can be observed in some schizophrenics in early childhood.

Researchers have made gallant efforts to understand and treat the disorder, which in two-thirds of cases is a lifelong problem. There is evidence that it is genetic, but no genes have been definitively linked to the illness. Harvard researchers have reported recently that people with schizophrenia have a significant shrinkage in an area of the brain involved in speech.

Patients seem to suffer a chemical imbalance in the brain, pumping out too much dopamine, a neurotransmitter that mediates mood and thoughts. It is still not well understood what effect environmental stress has on triggering the illness.

To most researchers, a viral explanation for schizophrenia seems absurd. After all, there have been no epidemics, and the incidence has always remained at about 1 percent everywhere in the world.

Still, Dr. Torrey has been hunting for identical twins whose genetics match but whose behavior has set them light years apart in an attempt to figure out what causes one of the two to escape the illness.

TTC If schizophrenia were solely a genetic illness, why does it occur in only 30 percent to 40 percent of the identical twins whose siblings have schizophrenia? Dr. Torrey reasoned that there must be a virus that could explain the difference.

He called Dr. Robert Yolken, a virologist at the Johns Hopkins University in Baltimore, and said he was sending over blood and cerebrospinal fluid samples from his study group.


Dr. Yolken would run them through tests designed to capture antibody activity against a number of different viruses. The body produces antibodies in response to foreign organisms, including viruses, and the antibodies remain present in the blood even after the virus is gone.

Dr. Yolken ran the samples against a virus that causes diarrhea in animals and also causes some neurological symptoms. The bug, BVDV (for bovine viral diarrhea virus), is a major cause of disease and death in cattle, pigs and sheep. No one has ever described this virus family in humans.

Until now.

Dr. Yolken took the twin study serum and exposed it to the BVDV. To his surprise, close to half the serum from the twins with schizophrenia made antibodies against the BVDV virus, compared to only one of the 50 normal subjects tested. It is also showing up in some twins with manic-depression.

"We don't know what we've got, but it is very interesting," Dr. Yolken said in a telephone interview. "It is very preliminary, and we need more studies."

Dr. Yolken said that the schizophrenic patients are probably not reacting to the BVDV virus, but one of any number of organisms found in the pesti family of viruses. These so-called retroviruses have not been described before in humans.


"I think we are looking at a chronic viral encephalitis," Dr. Torrey said. "If we are lucky, we are describing one of the viruses involved." He said that even if a virus is involved, it does not rule out genetic contributions.

The researchers have not yet found the virus itself in humans, although they are searching.