Premature birth may affect adult personality

Young adults who were born very prematurely tend to be more anxious and prone to depression than their peers, a new study suggests.

UK researchers found that among 18- and 19-year-olds, those who were born very prematurely - before the 33rd week of pregnancy - generally scored higher on a standard measure of “neuroticism.” That is, they were by nature more nervous, moody and lacking in self-esteem than their peers who were born full-term.

At the same time, the preterm group scored lower on a measure of extraversion, the tendency to be outgoing, assertive and sometimes risk-taking.

The findings, say the study authors, suggest that young adults born substantially early may be at higher-than-average risk of developing clinical depression and anxiety disorders. However, they report in the journal Pediatrics, the results are only preliminary, and any conclusions about the risk of mental health disorders “are necessarily speculative.”

For their study, Dr. Matthew Allin of King’s College London and his colleagues assessed 108 young men and women who were born before the 33rd week of pregnancy, along with 67 young adults who were born at term. A full-term pregnancy lasts about 40 weeks.

All of the study participants completed standard questionnaires that measure three dimensions of personality: neuroticism, extraversion and “psychoticism”—the tendency to be emotionally cold, aggressive and prone to antisocial behavior.

Overall, the preterm group had lower extraversion scores and higher neuroticism scores. The two groups scored similarly, however, on the measure of psychoticism.

A complex mix of genes and environment goes into forming an individual’s personality, and it’s not clear why premature and full-term children might have general differences in some traits, according to Allin and his colleagues.

Early injury to the brain could be one factor, they speculate, as may the influence of parents and peers as the children grow up. For example, parents of premature babies may be more protective from early on, which may contribute to the more cautious, introspective nature seen in these children.

On the other hand, the researchers point out, it’s not clear how important parenting style may be in adult personality. Studies of twins who were raised separately suggest that personality has a large genetic component.

It’s possible, Allin’s team speculates, that premature children are more likely than others to inherit certain personality traits. One recent study found that women with high anxiety levels during pregnancy were at increased risk of delivering prematurely - which suggests preterm infants might be more likely to inherit a tendency toward anxiety.

SOURCE: Pediatrics, February 2006.

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