PREMATURE babies are twice as likely to suffer from severe mental conditions like depression and bipolar disorder in adulthood as those born on schedule, a study has found.
Babies born at 36 weeks gestation or earlier had double the chance of being admitted to hospital for mental disorders as those born on term, while those born at 32 weeks or earlier had three times the risk, a study found.
Previous research had indicated preterm babies were more likely to have behavioural problems at school, but the new study of 1.3 million Swedish medical records found that the risk could extend into adulthood.
Researchers from King's College London examined the hospital records of 10,000 people who were admitted to hospital for depression, psychosis, bipolar disorder, eating disorders and alcohol or drug addiction.
They found that in adulthood, people who had been born very prematurely (less than 32 weeks gestation) were three times as likely to experience depression, 7.4 times as likely to have bipolar disorder, 2.5 times as likely to suffer from psychosis and 3.5 times as likely to develop an eating disorder.
Those born moderately prematurely (33 to 36 weeks early) had 1.3 times the chance of depression, 2.7 times the chance of bipolar disorder and 1.6 times the chance of psychosis.
Preterm babies' brains are more vulnerable to brain injuries because their nervous systems are less developed, which could explain their increased risk of mental disorders in later life, researchers said.
They said introducing routine tests for behavioural problems in five-year-olds could pick up developmental issues early, and argued that doctors should consider premature birth when making diagnoses of mental disorders in children up to the age of 18.
Dr Chiara Nosarti, lead author of the paper, said: "Since we considered only the most severe cases that resulted in hospitalisation, it may be that in real terms this link is even stronger.
"However, it is important to remember that even with the increased risk, these disorders still only affect one to six per cent of the population."