Diseases of the Mind.(scientists believe infections may play role in mental illness)

Olga Skipko has had the good fortune to live most of her adult life in the Polish village of Gruszki, in the heart of the Puszcza Bialowieska, one of Europe's most beautiful forests and home to wolves, lynxes and the endangered European bison. Unfortunately, the forest is also a breeding ground for disease-carrying ticks. Skipko, 49, thinks she was bitten about 10 years ago, when she began having the classic symptoms of Lyme borreliosis, a tickborne nervous-system disease: headaches and aching joints. She didn't get treatment until 1998. "I was treated with antibiotics and felt a bit better," she says.

That was only the beginning of her troubles. A few years later, she began to forget things and her speaking grew labored. It got so bad that she had to quit her job in a nursery forest and check herself in to a psychiatric clinic. "I hope they will help me," she says. "I promised my children that when I come back home, I will be able to do my favorite crosswords again." Doctors ran a battery of tests and concluded that her mental problems were the advanced stage of the Lyme disease she had contracted years ago.

Scientists have long known that some diseases can cause behavioral problems. When penicillin was first used to treat syphilis, thousands of cured schizophrenics were released from mental asylums. Now, however, scientists have evidence that infections may play a far bigger role in mental illness than previously thought. They've linked cases of obsessive-compulsive disorder, bipolar disorder and schizophrenia to a variety of infectious agents, and they're investigating autism, Tourette's and anorexia as well. They're beginning to suspect that bad bugs may cause a great many other mental disorders, too. "The irony is that people talked about syphilis as the 'great imitator'," says University of Louisville biologist Paul Ewald, "but it may be the 'great illustrator'--a model for understanding the causes of chronic diseases."

Mental illnesses constitute a large and growing portion of the world's health problems. According to the World Health Organization, depression is one of the most debilitating of diseases, on a par with paraplegia. Psychiatric illnesses make up more than 10 percent of the world's "disease burden" (a measure of how debilitating a disease is), and are expected to increase to 15 percent by 2020. Much of this may be the work of viruses, bacteria and parasites. Psychiatrist E. Fuller Torrey, of the Stanley Medical Research Institute in Maryland, has found from studying historical asylum records that hot spots--higher-than-normal incidences--of mental illness can shift, much like infectious-disease outbreaks, which lends credence to the notion that infectious agents play a big role. "Mental disorders are the major chronic recurrent disorders of youth in all developed countries," says Harvard policy expert Ronald Kessler, who directs the WHO's mental-health surveys.

Perhaps the most well known disease that's been linked to mental disorders is Lyme disease, which is caused by the Borrelia burgdorferi germ. First identified in the mid-1970s among children near Lyme, Connecticut, the disease has long been known to cause nervous-system problems and achy joints if left untreated. Now scientists are finding that Lyme disease can also trigger a whole smorgasbord of psychiatric symptoms, including depression. One New York man ...