Rare Childhood Infections Linked to Schizophrenia
> 1/8/2008 11:34:38 AM

The debilitating influence of schizophrenia has long been linked to genetic and environmental irregularities encountered by children in the periods directly before and after birth. Early in the 20th century, scientists noted a far greater instance of delusional symptoms in children born during the winter months, when the influenza epidemic and related infectious diseases held terrible sway over an unprepared populace. Schizophrenia itself was a new and very poorly understood condition at the time, but further research continued to link the disorder to abnormalities in the developing brain. Its causal factors remain somewhat uncertain in the present day, and longitudinal studies tracking the development of childhood infections are, in general, extremely rare. But with approximately 1% of the world population suffering from the ravages of schizophrenia and related psychoses, the demand for up-to-the-minute research has never been greater. Swedish researchers initiated a long-term study to examine the disorder's infectious connections, and their newly published results contradict some previous data in establishing a relationship between rare early-life infections and the subsequent development of delusional psychotic disorders.

Despite the uncertain nature of recent links drawn between popular suspect influenza and schizophrenia, experts across disciplines have established a clear link between prenatal infectious diseases and the eventual development of abnormalities including developmental disabilities, behavioral problems and mood disorders. In one example, we recently highlighted the possible connection between schizophrenia and the rare parasitic infection t.gondii. To counter the lack of definitive research on the connection, researchers collected the records of more than 1 million Swedes born between 1975 and 1983, focusing on the subsequent medical histories of the approximately 9,000 who'd contracted some form of CNS infection by the age of 12. Researchers combed this extensive database to determine the prevalence of nonaffective psychoses (mental illnesses unrelated to mood regulation) including dementia and schizophrenia. The conditions in question, divided into those of a viral and those of a bacterial nature, included the common (meningitis, encephalitis, influenza, herpes, rubella) and more obscure (mumps, enterocytopathogenic human orphan or nonparalytic polio virus).

Their collected numbers appear encouraging: just over 2,000 of the subjects included in the study suffered from some form of nonaffective psychosis, and 23 of these had experienced CNS infection. But from these small sums rise imposing percentages. Overall increases in diagnoses among patients with CNS infections equalled approximately 50%, and the numbers held true when applied strictly to schizophrenia. But two particular viruses created huge statistical shifts: the mumps and the cytomegalovirus (CMV). The former is now extremely rare thanks to the 1967 development of an effective vaccine. Approximately 1,000 cases of the mumps virus still arise in the United States each year, and patients are 2.7 times as likely to develop subsequent nonaffective psychoses, but the condition's influence is minor at best. CMV, on the other hand, is the most common cause of infectious brain damage in children when it's contracted in utero. And those who'd been diagnosed with CMV were more than 16 times as likely to develop a psychotic disorder later in life. The isolation of these two conditions implies that they affect the developing brain in specific ways to encourage the development of nonaffective psychotic conditions. CMV begins by infecting the white matter surrounding the brain, eventually moving into its operative areas to cause further structural damage.
This study, despite starting with more than 1 million subjects, produced numbers so small that drawing any definitive conclusion on the issue would be somewhat premature: of the 63 patients who contracted the CMV virus in early life, only 2 developed later cases of psychosis, and these patients had been infected postnatally. Further research drawing from an even larger subject pool may establish a definitive connection between some early-life infections and the development of schizophrenia, but current data remains, for the most part, inconclusive. The idea of prenatal influenza or other commonly harmless infections leading to schizophrenia and delusional psychosis has not been fully supported by contradictory research data. Genetics are the most obvious factor in the disorder's development: patients whose immediate relatives suffer from schizophrenia are more than 7 times as likely to develop the condition themselves. But examining its viral roots, even if those are rare, will help us develop future treatment solutions.

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