ScienceDaily (Mar. 6, 2007) — Girls born weighing less than 2,500 grams (about 5.5 pounds) may be more likely to develop depression between ages 13 to 16 than those born at a normal weight, while the same does not appear to be true for boys, according to a report in the March issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Several previous studies have linked low birth weight with depression in adolescence and adulthood, according to background information in the article. Some suggest that, like adult-onset diabetes or cardiovascular disease, the potential for depression may lie dormant in individuals born with low birth weight, emerging under stressful conditions. However, previous research has not considered differences in rates of depression by age and sex, the authors note.

Elizabeth Jane Costello, Ph.D., Duke University Medical School, Durham, N.C., and colleagues examined the association between low birth weight and depression in 1,420 participants between the ages of 9 and 16 years, 49 percent of whom were female. Children from 11 North Carolina counties were enrolled in the Great Smoky Mountains Study in 1993 and assessed yearly for depression and other psychiatric disorders during childhood (age 9 to 12) and adolescence (age 13 to 16 years). The children's mothers gave information about birth weight and other indicators of adversity, such as having a mother younger than age 18 at birth or having a parent who left school before the 11th grade.

A total of 5.7 percent of the girls in the study were born weighing less than 2,500 grams. Of those, 38.1 percent experienced at least one episode of depression between ages 13 and 16, compared with 8.4 percent of those born at a normal weight. The risk of depression attributable to low birth weight was 18 percent--in other words, if all female babies were born at a normal weight, 18 percent fewer teen girls would have episodes of depression. On average, 23.5 percent of teen girls with low birth weight were depressed each year, compared with 3.4 percent of those with normal birth weight.

The same effect was not observed in boys--throughout childhood and adolescence, no more than 4.9 percent of boys experienced depression, regardless of birth weight. Low birth weight was not associated with an increased risk of any other psychiatric condition, including anxiety disorders, in either boys or girls.

"The findings need replication in larger samples that include prospective data from birth to adulthood. Important next steps will include separate examination of the many different hormonal, morphological, psychological and social aspects of puberty that might best explain the increase in risk seen in adolescence, herein indexed by age," the authors conclude. "For the present, the findings suggest that pediatricians and parents of girls who were of low birth weight should pay close attention to their mental health as they enter puberty."

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