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Also (long quote ahoy):<small>We hardly think of syphilis as a mental illness today, but patients with syphilitic infection of the brain can suffer hallucinations, delusions, and mood changes not very different from those seen in bipolar disorder and schizophrenia. An early-tewntieth-century psychiatric text describes the mania-like excitement that was sometimes seen in persons with central nervous system syphilis: "The intensity of the excitement is extreme; there is absolute sleeplessness [and] incessant restlessness. The grandiose delusions are the controlling feature of the paretic's thought. The patient . . . comes before us tremulous with emotion, his eye bright, as the overpowering visions of wealth and grandeur float before his mind."[7] The discovery of reliable and effective diagnostic techniques for general paresis of the insane--unfortunately, arsenicals had little effect on the advanced central nervous system disease--was seen by many as an enormous advance in the understanding of psychiatric disorders. Clinicians charged with the care of psychiatric patients had great hopes that the causes of other psychiatric disorders would soon be found.</small>
Both excerpts from:<small>For many years there has been great interest in the possibility that viruses are in some way connection tp the development of psychiatric illnesses. Most of the work in this area has focused on the role of viruses in the causes of schizophrenia, but there is growing interest in the possibility that viral infections may have something to do with the causes of bipolar disorder as well.
Links between viruses and psychiatric illness have been sought in several different ways: (1) examining birth records to determine if persons with psychiatric illnesses tend to be born during times when viral infections are more common, (2) doing autopsy studies to look for virus particles in the brains of individuals with psychiatric illnesses, and (3) testing living individuals for immunological evidence of viral infections. All three of these methods have revealed the possibility of a link between bipolar disorder and certain viruses.
It has been well known for many years that persons with schizophrenia are somewhat more likely to have been born in the winter and spring months when viral infections are more common. A number of studies also suggest that there is an increased incidence of schizophrenia in children born during times of higher than usual rates of influenza, measles, and chicken pox. It has been suggested that viral infection of the developing brain during the third to seventh month of gestation may somehow lead to the development of schizophrenia in some people. Several studies have found that individuals with bipolar disorder are more likely to have been born in winter, suggestion that prenatal viral infections may have some role in the later development of bipolar disorder as well.[8]
Testing for evidence of viral infections by looking for viral DNA and RNA in the brains of individuals with bipolar disorder has become possible with the development of sophisticated biochemical techniques that allow tiny amounts of viral genetic material to be isolated and identified. As you probably know from the news coverage of criminal trials, DNA and RNA are unique molecular "fingerprints" that can identify individuals with great certainty. DNA and RNA can be used to "fingerprint" viruses in the same way. DNA and RNA from certain viruses have been found in the brain tissue of persons with bipolar disorder but have not been found, or have been found in lower concentration, in control subjects. These findings provide additional evidence that viral infection may be involved in some way with the development of bipolar disorder, at least in some individuals.[9]
A third method of investigating the possibility that viral infections are involved in the development of bipolar disorder is to test for antibodies to viruses by means of a blood test. Most blood tests for viral infestion, such as tests for HIV and hepatitis viruses, don't actually test for the virus itself but rather for chemical defenders called antibodies that the body produces in response to a viral infection. Each type of antibody is shaped precisely and uniquely to fit the invading organism that promted its manufacture. The presence of antibodies to a particular virus in the bloodstream indicates that the body has encoutered that particular virus before. Researchers using this approach have been investigating possible links between bipolar disorder and an animal virus called the Borna disease virus.
Borna disease, an illness that usually affects horses and sheep, is cuased by a virus that invades the brain and meninges (the covering tissues of the brain) of the animal and causes progressive deterioration in brain functioning and, eventually, death. The virus is not known to cause human illness, but antibodies to the Borna disease virus have been measured in healthy humans. Although most animals infected with the Borna disease virus develop the rapidly fatal brain infection, some laboratory animals experimentally exposed to the virus have been observed to develop a persistent but low-grade infection that does not cause rapid death. Some of these animals develop behavior changes that bear some resemblance to bipolar disorder: periods of overactivity and of progressive apathy and withdrawn behavior.
There have been a number of studies testing mood-disorder patients and control groups for the presence of antibodies to the Borna disease virus. Several of the studies have found that a higher proportion of the mod-disorder patients have these antibodies compared with the control subjects.[10] This suggests that, in some patients at least, a virus similar to the Borna disease virus may contribute to the development of mood-disorder symptoms. Perhaps there is an interaction between viral infection and genetic vulnerability that can result in a mood disorder. Other illnesses are known to result from this interaction of genetic vulerability and viral infection. For example, insulin-dependent diabetes, the severe form of diabetes that usually has its onset in childhood, is believes to occur when a combination of genetic facotrs and a viral infection brings about an abnormal immune reaction, causing the destruction of the insuling-producing cells of the pancreas. Perhaps a similar mechanism operates to cause some cases of mood disorders.</small>
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