A number of studies have indicated a relationship between breastfeeding and meeting developmental milestones and cognition. Some studies have also indicated that breastfeeding may be associated with psychological and behavioural outcomes but the methodologies have been questioned. A study was carried out in Australia to determine whether there was an independent effect of breastfeeding on child and adolescent mental health. A total of 2,900 pregnant women were recruited and those having live births were followed up for 14 years. Mental health status was assessed using a validated tool at 2, 6, 8, 10 and 14 years. The tool allowed for assessment of “internalised” issues such as being withdrawn, anxious/depressed and for “externalised” issues such as delinquent or aggressive behaviour. Maternal confounders such as age, education, smoking, family income, family structure, life stress events and depression were taken into account. The researchers found that breastfeeding for less than 6 months compared with 6 months or more was an independent predictor of mental health problems, both internalised and externalised through childhood and into adolescence. The researchers recommend interventions aimed at increasing breastfeeding duration as this could be of long term benefit for child and adolescent mental health.

Oddy WH, Kendall GE, Li J et al (2009) The Long-Term Effects of Breastfeeding on Child and Adolescent Mental Health: A Pregnancy Cohort Study Followed for 14 Years. Jpeds. Vol 156, Issue 4, 568-574