Being born very premature can affect a child's personality into adulthood, a study has suggested.
The researchers looked at babies born before 33 weeks
Researchers from the Institute of Psychiatry studied 18 and 19-year-olds who had been born early, and compared them to those born at full-term.
Premature babies, particularly girls, were found to be more likely to be anxious and withdrawn, and potentially at a higher risk of depression.
The study is published in the American journal Pediatrics.
The researchers assessed 108 young adults who had been born before 33 weeks gestation between 1979 and 1981.
They were then compared with 67 people of the same age who were born at full-term.
Everyone was asked to complete a personality questionnaire, which included 48 questions such as 'does your mood ever go up or down?' and 'do you enjoy co-operating with others?'.
The results suggested those born prematurely had lower levels of a personality trait called 'extraversion', indicating that they may have less confident and outgoing personalities.
They also had higher levels of the personality trait 'neuroticism', which indicates increased anxiety, lower mood and lower self-esteem.
Girls' personalities were more likely to be affected by being born early.
The researchers, led by psychiatrist Dr Matthew Allin, said the scores suggest being born very premature might predispose someone to the kind of personality likely to develop depression and anxiety disorders.
The study did not look at why being born premature might affect personality.
But Dr Allin told the BBC News website there were a few possible explanations.
"It's possible that being born very small might be linked to some damage to the brain, possibly an infection.
"It might be that being in an incubator makes it difficult to bond with parents, and for them to bond with you.
"While another possibility is that personality is in the genes to some extent, so could be inherited to some degree."
The researchers plan to continue their studies to try to pin down which explanation is correct.
A spokeswoman for Bliss, the premature baby charity, said: "These findings are very interesting.
"Instead of attributing these findings exclusively to brain function, genetics or upbringing, we would like to see more research into the stress and trauma caused by the intensive care experience itself.
"The possible effects of psychological trauma stemming from something highly invasive, like intensive care, should not be ignored. This is an area which merits much more research and attention."