Underweight babies are more likely to be 'neurotic adults', new research suggests
Babies born very prematurely or severely underweight are at an increased risk of becoming introverted, neurotic and risk averse as adults, research suggests.
Scientists say such a personality profile could help explain the higher rates of career and relationship difficulties experienced by this group in later life.
The study, by the University of Warwick, followed 200 German adults born between 1985 and 1986 either very prematurely or with a birthweight below 1.5kg (3lb 5oz)
A similar number of adults born at full term and at a normal weight also provided the team of researchers with information about their personality traits.
These were assessed across five criteria - introversion, neuroticism, levels of openness to new experiences, agreeableness and conscientiousness.
Adults who had been born very prematurely and underweight scored significantly higher on all but two of the personality traits - conscientiousness and openness.
They also reported significantly higher levels of autistic spectrum behaviours, along with lower levels of risk taking.
Researchers say these traits describe a "socially withdrawn" personality, or someone who is easily worried, less socially engaged, less interested in taking risks and less communicative.
Professor Dieter Wolke, of the department of psychology, University of Warwick, led the research, which is published in Archives of Disease in Childhood: Fetal & Neonatal Edition.
"Personality characteristics are very important because they help people to develop into adult roles and form and maintain social relationships," Prof Wolke said.
"Very premature and very low birth weight adults who have a socially withdrawn personality might experience difficulty dealing with social relationships with their peers, friends and partners.
"Defining a general personality profile is important because this higher order personality factor may help to partly explain the social difficulties these individuals experience in adult roles, such as in peer and partner relationships and career.
"Previous studies have found they are more likely to be bullied at school and less likely to progress to university or attain well paid employment.
"They are also less likely to form social contacts, to maintain romantic relationships and to have children.
"If identified early parents could be provided with techniques to foster their child's social skills to help compensate for socially withdrawn personality characteristics."
Some participants in the research are in the Bavarian Longitudinal Study, which tracks the health and wellbeing of children born in 1985 and 1986 and admitted to hospital within 10 days of birth.
Others were those born full term in the same maternity units over the same timeframe.
Very premature births at less than 32 weeks and a birthweight of less than 1.5kg are known to be linked to an increased risk of autistic spectrum behaviour.
However, it has not been confirmed how prematurity and low birthweight might affect other personality traits in adulthood.
Researchers compared the personality traits of 200 26-year-olds who were born prematurely and severely underweight with 197 young people who had been born at term and a normal weight range.
Their results were not sex-specific, related to income or education.
In the paper, Prof Wolke writes that the higher scores of very premature and low birthweight adults are likely to be the result of alterations in brain structure and functioning.
Previous studies have linked poor peer relations and social-emotional problems in childhood with regional disruptions in the white matter in the right orbital frontal cortex.
This region is involved in social regulations and social cognition.
Early stresses experienced in the womb, and having over-protective parents, are also thought to be possible factors in a withdrawn personality.
Evidence showed that many adults born very prematurely or with a low birthweight are less likely to go on to higher education or get well paid jobs.
They are also at a higher risk of finding it harder to make friends, find long term partners and become a parents, the researchers added.