People whose mothers showed depressive symptoms during pregnancy had an increased risk for depression themselves at age 18, a long-running British cohort study indicated.

Prenatal depressive symptoms were an independent risk factor for depression in adult offspring with an odds ratio of 1.23 (95% CI 1.03-1.44) for each standard deviation of increase in prenatal depression scores on a self-reported instrument, after adjusting for a variety of potential confounding variables, according to Rebecca M. Pearson, PhD, of the University of Bristol in England, and colleagues.

Findings in the longitudinal study of more than 4,500 parents and their young-adult children indicated a trend toward increased depression risk in the offspring associated with postnatal maternal depression, but it did not reach statistical significance (adjusted OR 1.13, 95% CI 0.94-1.34), per standard deviation in maternal depression score.

Maternal education appeared to be a significant factor affecting the relationship between postnatal depression (but not prenatal depression) and risk in the children, the researchers reported online in JAMA Psychiatry.

Although the study did not evaluate the effects of maternal depression treatment on offspring depression risk, Pearson and colleagues argued that the results “suggest that treating depression in pregnancy ... may be most effective” for preventing the illness in their children.

Previous studies have linked depression in adolescents to postnatal depression in their mothers, but the potential contribution of depression during pregnancy has not been well studied, the researchers explained.

Elizabeth Corwin, PhD, RN, of Emory University School of Nursing in Atlanta, told MedPage Today that the study results were “exciting” because they help to fill this gap, and did so with a study sample large enough to support detailed statistical analyses.

But she suggested that the researchers’ conclusion regarding benefits of maternal treatment for offspring may have been an over-reach.

“They do not address whether or not it will alleviate [offspring depression], had no impact, had any impact,” Corwin said.

“Other researchers have looked at the same problem, and it is hard to tease out women who have been treated compared to those who have not, and the effects on offspring. This is a difficult area.”

In the study, Pearson and colleagues analyzed data from the Avon Longitudinal Study of Parents and Children. This project enrolled pregnant women in the Avon area of southwestern England who had predicted delivery dates from April 1991 to December 1992.

A total of 15,247 pregnancies were initially registered, but pre- and postnatal depression was assessed in only 8,937. Follow-up data on offspring at age 18 were available for 4,566. Paternal depression data were collected in 2,475 cases.

Maternal depression was assessed with the Edinburgh Postnatal Depression Scale (EPDS), a 10-item questionnaire administered to participants before and after delivery, yielding a score of 0-30 with 12 considered the threshold for significant depression. Depression in offspring was measured with the Clinical Interview Schedule (revised version) to produce a simple yes/no for the presence of major depression.

In univariate analysis of EPDS scores against the presence or absence of depression in offspring, prenatal depression was a significant risk factor with an odds ratio of 1.28 (95% CI 1.08-1.51) for each standard deviation in EPDS score. Postnatal depression was also significantly associated with offspring depression in the univariate model (OR 1.24, 95% CI 1.10-1.44).

However, such maternal factors as age, parity, social class, education, previous history of depression, smoking during pregnancy, breastfeeding, and others reduced the strength of these associations—slightly in the case of prenatal depression, which remained a significant risk factor, but markedly for postnatal depression.

When Pearson and colleagues stratified the sample by maternal education, those with below-median educational attainment did show a significant association between postnatal EPDS score and offspring depression (OR 1.26, 95% CI 1.06-1.50, per standard deviation in EPDS). No association was evident in those with high education levels.

In contrast, prenatal depression was significantly linked to offspring depression irrespective of maternal education.

Paternal depression appeared to have no influence on the child’s depression risk.

Because the study found different relationships with offspring depression for prenatal versus postnatal maternal depression, Pearson and colleagues suggested that these forms of maternal depression affect the child through different pathways. They argued that prenatal depression may affect the fetus biologically in utero, whereas postnatal depression may be “transmitted” primarily through differences in the home environment and social support.

On the other hand, the researchers acknowledged that the findings may reflect “shared genetic risk.”

Limitations to the study included the large number of children lost to follow-up and the absence of maternal depression measures during the children’s adolescent years.

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By John Gever, Deputy Managing Editor, MedPage Today

Source reference: Pearson R, et al “Maternal depression during pregnancy and the postnatal period: Risks and possible mechanisms for offspring depression at age 18 years” JAMA Psychiatry 2013; DOI: 10.1001/jamapsychiatry.2013.2163