Certain events during pregnancy may disrupt brain growth in ways that markedly raise a child’s likelihood of developing schizophrenia as a young adult, according to new results from three independent, long-term studies.
Periods of oxygen deprivation in the fetus and second-trimester respiratory infections in the mother exhibited strong associations with adult schizophrenia in these investigations. Maternal obesity before pregnancy also foreshadowed many cases of adult schizophrenia. Genetic traits, such as low concentrations of substances in the brain that help to protect oxygen-starved neurons, probably contribute to many cases of this severe psychiatric disorder, the research teams all say.
In the past 12 years, evidence for prenatal influences on schizophrenia has come primarily from analyses of medical data gathered at and soon after births in several European countries (SN: 2/3/96, p. 68). Results have been inconsistent. Studies have separately linked schizophrenia to several prenatal conditions: oxygen deprivation, malnutrition, infection, and maternal immune reactions.
The three new investigations tracked participants born in the United States in the late 1950s and early 1960s, beginning with their mothers’ entry into prenatal care and ending at age 35 to 40. Extensive biological and psychological measurements from mothers and their offspring at various ages were probed for statistical links to potential childhood risk factors for schizophrenia and diagnoses of the disorder later in life.
All the results appear in the current Schizophrenia Bulletin (vol. 26, no. 2). Schizophrenia, a break-up of thought and emotion that includes hallucinations and social withdrawal, often begins in young adulthood.
“These [new] studies may lead to environmental interventions that reduce the risk of schizophrenia, even before researchers gain a precise understanding of how environmental events interact with the genes involved,” contend Richard Jed Wyatt of the National Institute of Mental Health in Bethesda, Md., and Ezra S. Susser of Columbia University in an introduction to the reports.
Wyatt and Susser directed an analysis of lifelong medical data for 12,094 individuals treated in northern California, 71 of whom developed schizophrenia. The researchers found that mothers’ obesity before getting pregnant and infection by respiratory viruses in the second trimester of pregnancy had occurred much more often in cases of eventual schizophrenia than in the others. These results held after the scientists took into account the mothers’ age, education, and cigarette smoking history.
Maternal obesity may alter glucose metabolism and blood clotting and thus affect fetal brain growth, the scientists theorize. Mothers’ immune responses to particular infections may also disrupt fetal brain processes, they propose.
In a second study, led by Tyrone D. Cannon of the University of California, Los Angeles, pregnancy complications known to deprive the fetus of oxygen exhibited a pronounced link to adult schizophrenia. Disturbances of coordination, thinking, language, and social functioning appeared by age 7 in most people later diagnosed with the disorder.
Cannon’s team analyzed data on nearly 8,000 people whose mothers received prenatal care at either of two Philadelphia hospitals. Schizophrenia turned up in 72 of those studied.
The third study, directed by Ming T. Tsuang of Harvard Medical School in Boston, tracked people at high risk for schizophrenia because of either prenatal oxygen deprivation or having parents with the disorder. The participants displayed deficits in perceptual and motor skills, academic achievement, and general intelligence at age 7, the scientists report. They focused on about 12,000 people born in New England.