Girls who were born extremely prematurely may be at an increased risk of depression from childhood through young adulthood.
Using Finnish birth and health registers, the researchers examined 37,682 people diagnosed with mild, moderate, or severe depression and compared them to 148,795 healthy controls. The children were born between 1987 and 2007 and their mean age at diagnosis was 16 years.
After adjusting for age, depression, substance abuse, smoking, socioeconomic status, and other parental factors, they found that in girls, but not boys, younger gestational age is strongly linked to the diagnosis of depression in childhood, adolescence, or young adulthood was. Girls born before 28 weeks of gestation were about three times as likely to develop depression as girls born into full pregnancy. After 28 weeks of gestation the association was no longer significant. The study is in the Journal of the American Academy of Child & Adolescent Psychiatry.
The authors suggest that the limited age range in the study of 5 to 25 years means that primarily early-onset depression was identified, and this may underestimate the effect in boys who are typically diagnosed with depression in old age.
"This is a huge sample," said a co-author, Dr. Andre Sourander, professor of child psychiatry at the University of Turku in Finland, "and we had a lot of covariates for mothers and fathers." Even after considering all of these other factors that can contribute to depression, "the results remained significant," he said.