One of the largest studies to investigate birth complications and later mental health has found that premature birth (less than 32 weeks gestation) constitutes a single, independent risk factor for a range of severe brain and behavior disorders. Researchers at the Institute of Psychiatry at King’s College London and Karolinska Institutet in Sweden suggest that neurodevelopmental differences in those born prematurely may be important in understanding the link.

The study appeared online June 1 in the Archives of General Psychiatry, a publication of the American Medical Association. NARSAD Young Investigator Grantee Chiara Nosarti, PhD, of the Department of Psychosis Studies in the Institute of Psychiatry at London's King's College, led the study. Previous research has shown an association between premature birth and an increased risk of schizophrenia, but this is the first study to report an association with a broad range of psychiatric disorders, including bipolar disorder, psychosis and depression.

Dr.  Nosarti said "we found a very strong link between premature birth and a range of psychiatric disorders. Since we considered only the most severe cases that resulted in hospitalization, it may be that in real terms this link is even stronger. However, it is important to remember that even with the increased risk, these disorders still only affect 1-6% of the population."  The researchers found that individuals born very prematurely were three times more likely to be hospitalized with a psychiatric disorder aged 16 years and older, compared to those born at term (37-41 weeks gestation). The risk varied depending on the condition - for psychosis it was 2.5 more likely, for depression three times more likely and for bipolar disorder 7.4 times more likely. The findings also revealed a smaller increased risk for those born moderately prematurely (32-36 weeks).

Read More about this research on CNN

UPDATE: Read new article from the New York Times (July 2, 2012)