Adults who were born very prematurely, or with a very low birth weight, are more likely to have a socially withdrawn personality and show signs of autism, a new study has found.

UK researchers followed the progress of 200 adults who were either born very prematurely (before 32 weeks gestation), or had a very low birth weight (less than 1.5kgs/3lbs, 4oz).

All were born in the mid-1980s and they were compared with a similar number of adults who were born at full term with a normal birth weight.

The study found that those who were born very prematurely, or with a very low birth weight, were much more likely to be socially withdrawn as adults. They were also more likely to display signs often associated with autism, such as introversion and decreased risk taking.

The results stood even when other factors were taken into account, such as gender, education and income.

"Personality characteristics are very important because they help people to develop into adult roles and form and maintain social relationships. Very premature and very low birth weight adults who have a socially withdrawn personality might experience difficulty dealing with social relationships with their peers, friends and partners," commented lead researcher, Prof Dieter Wolke, of the University of Warwick.

He suggested that early stresses experienced in the womb, or having parents who are over-protective, could contribute to a withdrawn personality.

He noted that previous studies have suggested that people with withdrawn personalities are more likely to be bullied in school and are less likely to go on to third level education or get a well-paid job.

"They are also less likely to form social contacts, to maintain romantic relationships and to have children. However, if identified early parents could be provided with techniques to foster their child's social skills to help compensate for socially withdrawn personality characteristics," Prof Wolke said.

Details of these findings are published in the journal, Archives of Disease in Childhood: Fetal & Neonatal Edition.