Researchers at Sweden's Karolinska Institute have found a link between premature births and mental illness.
The study involving more than 500,000 infants found that preemies were twice as likely to be admitted to hospital for a psychiatric disorder in their early 20s than those born at full term.
Almost 5.5 per cent of those born very early had been admitted to hospital for a psychiatric disorders such as mood disorders, stress-related complaints and suicide attempts or deaths, compared to 2.4 per cent of those born at full-term.
"Pre-term birth carries some risk for psychiatric disorders requiring hospitalisation in adolescence and young adulthood," The Sydney Morning Herald quoted the researchers as saying.
During the study, the researchers tracked premature babies born from 1973 to 1979 through their medical records.
Infants, who were born at 33 to 36 weeks, were at risk with three per cent having been admitted to hospital for a psychiatric disorder.
Sydney University's Brain and Mind Research Institute executive director Professor Ian Hickie said that premature birth disrupts a critical phase of brain development in the mid to late stages of pregnancy.
"If you're born prematurely it's likely that in some time that period of brain development is interrupted," he said.
"So the critical brain connections and the critical brain pathways are probably harmed by premature birth.
"The effect on some of those brain pathways is probably continued throughout brain development," he added.
Prof Hickie said that focussing on maternal health would decrease the likelihood of prematurity,
"There are some really common issues like smoking in pregnancy and alcohol use in pregnancy which continue to be common and contribute to premature birth and difficulties in the womb," he said.
The study is published in the journal Paediatrics.