Risk of mental illness higher for premature babies

Babies born prematurely are at significantly increased risk of developing mental health disorders such as psychosis, depression, and bipolar disorder as adults, according to a new study.

Compared to babies born at full term, which is 37 to 42 weeks of gestation, babies who were born at less than 32 weeks were 7 times more likely to be hospitalized with bipolar disorder as adults.  They were three times more likely to be hospitalized for depression and more than twice as likely for psychosis according to the study.

People born between 32 and 36 weeks also suffered from mental health conditions as adults, but with less severity than those born more prematurely.  The research was published in the Archives of General Psychiatry.

Scientists analyzed data from the medical records of more than 1.3 million people born in Sweden, focusing on people older than age 16 who were admitted to a hospital for a psychiatric disorder. The researchers then looked to see who had been born prematurely.

Experts aren't exactly sure why people who were born prematurely had more mental health issues than people who were carried to term as babies.. They suspect it's due in part to a kind of brain injury resulting from an immature nervous system. The brain wiring or connections may not be as robust or well developed as in full term babies. The premature infants also are bombarded with environmental stressors they would not experience if still in the womb and this could inhibit normal development, scientists suggest.

And these new babies are in incubators instead of their parent's arms where bonding occurs, says Dr. Michael Katz, Interim Medical Director for the March of Dimes and a retired pediatrician.

"The external circumstances may be stressful enough that it can cause [mental health] problems," explains Katz.

Previous research has shown that premature babies have a wide range of health and developmental problems, but this is one of the first studies to look at the relationship between premature births and severe psychiatric disorder.