Premature babies are significantly more likely than average to suffer serious mental disorders, such as schizophrenia, in later life, a study has found.
The risk is greatest for those born following a pregnancy lasting less than 32 weeks. Compared with normal term babies, they are three times more likely to be hospitalised for a psychiatric problem at age 16 or older, researchers found.
Very premature babies have more than twice the normal chance of developing schizophrenia and other forms of psychosis.
Their risk of bipolar disorder is increased more than seven-fold, while the chances of developing major depression and eating disorders are raised 2.9 and 3.5 times.
Experts stressed that the chances of a premature baby having a serious psychiatric problem were still small.
Rates of hospitalisation for psychosis are raised from two in 1,000 to around four in 1,000. The vast majority of pre-term babies turn out healthy and normal -- famous examples including Sir Winston Churchill and Albert Einstein.
Researchers believe the pattern is due to the impact of being born prematurely on early brain development. However, why some children are affected and others not is unknown.
The research, reported in the Archives of General Psychiatry, is based on a study of almost 1.5 million Swedish birth and medical records from 1973 to 1985.
Every child admitted to hospital with a first episode of a psychiatric disorder by 2002 was identified.