Michael S. Kramer, M.D., of McGill University and the Montreal Children's Hospital, Montreal, Quebec, and colleagues conducted a randomized trial of a breastfeeding promotion program involving patients at 31 maternity hospitals and affiliated clinics in Belarus. Between June 1996 and December 1997, clinics were randomly assigned either to adopt a program supporting and promoting breastfeeding or to continue their current practices and policies. A total of 7,108 infants and mothers who visited facilities promoting breastfeeding and 6,781 infants and mothers who visited control facilities received follow-up interviews and examinations between 2002 and 2005, when the children were an average of 6.5 years old.

Even though the treatment difference appears causal, it remains unclear whether the observed cognitive benefits of breastfeeding are due to some constituent of breast milk or are related to the physical and social interactions inherent in breastfeeding, the authors write. Essential long-chain fatty acids and a compound known as insulinlike growth factor I, both found in breastmilk, could be responsible for the cognitive differences. On the other hand, the physical or emotional component of breastfeeding may lead to permanent changes affecting brain development. Breastfeeding also may increase verbal interaction between mother and child, which could improve children's cognitive development.

Although breastfeeding initiation rates have increased substantially during the last 30 years, much less progress has been achieved in increasing the exclusivity and duration of breastfeeding, the authors conclude. The consistency of our findings based on a randomized trial with those reported in previous observational studies should prove helpful in encouraging further public health efforts to promote, protect and support breastfeeding.

(Arch Gen Psychiatry. 2008;65[5]:578-584. Available pre-embargo to the media at http://www.jamamedia.org/.)

Editor's Note: This research was funded by a grant from the Canadian Institutes of Health Research. Dr. Kramer is the recipient of a Senior Investigator Award from the Canadian Institutes of Health Research. Co-author Dr. Platt is a Monat-McPherson Career Investigator of McGill Unviersity and a career investigator of the Fonds de la recherche en santé du Québec. Co-author Dr. Fombonne holds a Canada Research Chair in Child Psychiatry. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.