Deprived of Breastfeeding in Infancy, Vulnerable to Severe Depression in Adulthood

Though pediatricians and public-health officials have fought to increase the practice of breastfeeding, their efforts have often proven fruitless in a world of out-of-wedlock childbirths and out-of-home maternal employ­ment. And unfortunately, evidence continues to mount that children deprived of breastfeeding in infancy pay a price later on. The latest evi­dence comes from a study in Brazil finding distinctively high levels of psychological problems among adults who were not breastfed as babies.

Published by researchers at the Federal University of Pelotas and the Universidade Católica de Pelotas, both Brazilian institutions of higher education, this new study probes the long-term effects of breastfeeding. The scholars conducting the study acknowledge that previous research has already established that individuals breastfed as babies are signifi­cantly less vulnerable to “behavioral and internalization problems, psy­chological stress, and depressive/anxiety symptoms” than are individuals who were not breastfed during infancy.

More particularly, the researchers recognize prior studies conclud­ing that, compared to individuals who were not breastfed during infancy, those who were breastfed achieve better performance on cognitive tests, manifest fewer behavioral and internalization problems, suffer from less psychological stress, and prove more resistant to depression, anxiety, and attention deficit disorder (ADD).

But the authors of this new study launch their inquiry because studies evaluating the effect of breastfeeding on “specific mental health disorders are scarce” and because some earlier studies “have failed to observe an association between breastfeeding and later mental health.” Desirous of filling the gaps and resolving the inconsistencies in the previ­ous research on the matter, the Brazilian scholars set out “to assess the association between breastfeeding and mental health outcomes in young adults.” To that end, the researchers parse data collected in 2012-13 from 3,657 individuals born in Pelotas in Southern Brazil in 1982, assessing these data in the context of information on breastfeeding collected for these individuals when they were young children.

When analyzing their data for simple binary associations, the researchers find that those who had been breastfed for less than one month were more vulnerable to common mental disorders (CMD), major depression (MD), and severe depression than were those who had been breastfed for at least six months. The Pelotas scholars then reassess their data in a more sophisticated multivariable statistical model (one account­ing for the possible influence of factors such as birth weight, maternal smoking during pregnancy, and parental psychiatric problems). In this multivariable statistical model, the likelihood that young adults who were not breastfed would develop common mental disorders or major depression at rates seen among peers who were breastfed fell below the threshold of statistical significance. Even in this model, however, young adults who had not been breastfed were still significantly more likely to suffer from severe depression than were their breastfed peers.

“In summary,” the researchers remark, “our findings suggest that breastfeeding reduces the odds of having more severe depressive symptoms.”

The researchers theorize that “the effect of breastfeeding over other mental health outcomes [such as common mental disorders and major depression] might be small,” too small to establish a significant associa­tion in a study limited by the number of individuals involved.

Looking at their overall results, the researchers remark, “[W]e believe that our findings suggest that breastfeeding is associated with mental health in early adulthood, specially depression or depressive symptomatology.”

Though they acknowledge inconsistency in the findings of previous research on the matter, the authors of this new study interpret their con­clusions in light of “studies [that] show the protective effect of breastfeed­ing over outcomes like general behavior or mental well-being, in chil­dren and adolescents.” In particular, the researchers find relevant a 1998 study finding that “among [children and adolescents] who were never breastfed, the odds of having major depression were higher, even in fully adjusted models.” Likewise relevant, in their view, was a 2012 study concluding that among adults “the odds of being depressed were higher among those breastfed for less than 2 weeks” than among those who were breastfed for at least six months.

The Pelotas scholars tentatively identify as “a possible path­way explaining the association between breastfeeding and mental health . . . the relationship between breastfeeding and cognitive devel­opment.” This pathway seems plausible given that social scientists have shown that “children with lower IQ have an increased risk of developing adult depression” and that “breastfeeding is associated with a higher IQ.”

The researchers discern a second possible explanation of the linkage between breastfeeding and mental well-being in earlier “studies [that] suggest that home environment and/or maternal care during childhood could influence the appearance of later mental health disorders and that breastfeeding is associated with [favorable] parent-child qualities.”

Lamentably, adverse trends in family life around the world are put­ting more and more babies in homes where mothers’ marital or employ­ment status makes sustained breastfeeding unlikely. That is good news only for those seeking full employment for psychiatrists and psychotro­pic drug manufacturers.

(Christian Loret de Mola et al., “Breastfeeding and Mental Health in Adulthood: A Birth Cohort Study in Brazil,” Journal of Affective Disorders 202 [2016]: 115-19.)