Premature birth appears to be related to hospitalizations for a range of psychiatric illnesses as the child becomes an adult, including depression and bipolar disorder, a recent study found.
The study, which was published in the June issue of Archives of General Psychiatry, examined about 1.3 million babies born in Sweden between 1973 and 1985. The researchers found that being born early was associated with an increased chance of admittance as an adult to the hospital for psychiatric conditions.
"I don't think this paper should be a cause for concern for women who have a baby who was born premature," said Dr. Ann Borders, assistant professor of obstetrics and gynecology atNorthwestern University's Feinberg School of Medicine. "I feel like it is more a call to the research community to continue to look at this association to better understand the connections between being born premature and adult onset of disease."
The question researchers need to ask, Borders said, is whether the association between premature birth and a higher risk of psychiatric illness is caused by the shorter time the fetus spent in the womb before birth or whether factors such as inflammation or chronic stress that can cause premature birth are responsible.
The researchers looked at the records of babies born in Sweden who were still living in Sweden at age 16 or by December 2002. Researchers then used data from the country's National Board of Health and Welfare to determine which of these babies eventually became hospitalized with psychiatric illnesses after they reached the age of 16.
Babies born between 32 to 36 weeks of gestation in the womb were 60 percent more likely than those between 37 and 41 weeks to eventually develop a psychosis, 34 percent more likely to eventually develop a depressive disorder and more than twice as likely to eventually develop bipolar disorder, the study found.
Babies born at less than 32 weeks had more than twice the risk than those born between 37 and 41 weeks of eventually suffering from a psychosis, nearly three times the risk of depression, and more than seven times the risk of bipolar disorder. Babies born at less than 32 weeks, who doctors call very premature, also had three times the risk of those born between 37 and 41 weeks of later being hospitalized for an eating disorder.
"It gives us an interesting finding that associates neurodevelopment or abnormal neurodevelopment potentially with being born prematurely," Borders said.
But she stressed that the study's findings don't mean "that if you are born prematurely that you are going to suffer from psychiatric illness necessarily."
Dr. Mina Dulcan, head of child and adolescent psychiatry at Ann & Robert H. Lurie Children's Hospital of Chicago, said that the study's findings about Swedish babies may not be fully applicable to babies born in the U.S. Sweden has a more ethnically homogenous population than the U.S, said Dulcan, who added that the U.S. also has more low-income people. Moreover, most mothers-to-be in Sweden receive prenatal care, "which would not be true in this country," she said.
Still, "for what it is, it's very well done," Dulcan said of the study.
The study's authors noted in the paper that they did not examine many factors that might help explain the association found between premature birth and future hospitalization for psychiatric illness such as ethnicity, socioeconomic status, family history of a previous premature delivery, smoking, substance abuse and viral infections. The study also only looked at youths and young adults who were admitted to a hospital with a mental illness. It did not include young people who had a psychiatric disorder who did not require hospitalization.
"These were the people who had severe depression, severe issues," Borders said. "Now it might have been, if you were able to account for everyone who has depression, we would never (have) this finding. ..."
Future studies should try to pinpoint the causes of premature labor among mothers in order to more specifically isolate a link between prematurity and future mental illness, Borders said.
It's important to do research like the Swedish study, Dulcan said.
"Eventually if we could come to understand how these disorders developed, we could develop better methods of prevention and better methods of treatment," she said. "Right now, pretty much most of our treatments (for psychiatric disorders) are symptomatic, but if we really understood what went wrong, we could do much better."