The incidence of schizophrenia was increased in the offspring of mothers who were in the early stages of pregnancy during the 1967 Arab-Israeli War, according to findings published in the medical journal BMC Psychiatry.
"Schizophrenia has been linked with intrauterine exposure to maternal stress due to bereavement, famine and major disasters," co-author Dr Dolores Malaspina of New York University School of Medicine and colleagues write.
According to recent evidence, the first three months of pregnancy may be the time of greatest vulnerability. Studies with rodents also suggest the sex of the fetus influences the outcome after stress exposure.
How the study was doneA total of 637 subjects with schizophrenia-related diagnoses and 676 with other psychiatric disorders were identified. Individuals with schizophrenia were more than twice as likely to be born in January 1968, which would put their mothers in the second month of pregnancy during June 1967.
The researchers evaluated offspring whose mothers were pregnant during the Arab-Israeli War, focusing on the month of pregnancy and the sex of the offspring. Birth records of 88 829 subjects born in Jerusalem between 1964 and 1976 were linked to Israel's Psychiatric Registry.
The increased incidence of schizophrenia was also about four times greater in females than in males. The risk for other psychiatric disorders was also 2.5-times higher among those in the third month of fetal life in June 1967. Again, the risk was greater in females than in males.
"Our study added to the very strong and accumulating evidence that maternal psychological stress alone (without infection, malnutrition, or other physical prenatal adversity) can have lasting effects on the health of the offspring," Malaspina said. "Some of these health effects may not show up for many years, such as schizophrenia."
She noted that a number of animal studies show effects of prenatal stress on the behavior and metabolism of offspring. "These changes may reflect an evolutionary benefit of adjusting the behavior or metabolism of an offspring that will be born during a stressful period," she explained.
"Clearly schizophrenia is not adaptive, but perhaps prenatal stress is acting to make someone more sensitive to potential threats or more vigilant," Malaspina suggested. "These might be the intended effects that increase the risk for schizophrenia." - (Reuters Health, October 2008)