Children who are exclusively breastfed during their first six months of life show lower risks of ADHD symptoms, a new study has found.

Researchers at the University of Bergen in Norway found an association between how long mothers breastfeed and the likelihood of their child developing ADHD symptoms.

“It is well established that psychiatric symptoms and disorders can be influenced by both genetic and environmental factors,” said Berit Skretting Solberg, a psychiatrist and researcher at the Department of Biomedicine, University of Bergen, and senior consultant at Betanien Hospital.

“We found that the longer a child was exclusively breastfed (up to six months), the lower the level of ADHD symptoms at ages three, five, and eight years,” added Solberg.

The researchers analysed data from more than 37,000 children born in Norway between 1999 and 2009, tracking breastfeeding patterns and following up at ages three, five and eight.

They found that any breastfeeding was associated with reduced ADHD symptoms, but the effect increased with both the duration and intensity, peaking with exclusive breastfeeding up to six months.

The study also found significant differences between the sexes, with girls showing the strongest associations at all ages.

Solberg noted that while heredity is probably the strongest risk factor for ADHD, neurodevelopmental disorders are shaped by multiple factors.

Attention deficit hyperactivity disorder (ADHD) is a behavioural and neurodevelopmental condition characterised by inattention, hyperactivity and impulsivity. It is usually diagnosed during childhood.

There is no cure for ADHD, but treatments include behavioural therapy and medication.

Breast milk is the primary food source for several months for most children. The World Health Organization and UNICEF recommend breastfeeding within the first hour of birth and for children to be exclusively breastfed for the first six months of life, meaning no other foods or liquids — including water — are provided.

The researchers suggest several biological mechanisms may explain the link. Breastmilk contains macronutrients, vitamins, pre- and probiotics, immune components and other biologically active components that can shape brain development in early life.

Despite these benefits, many women do not breastfeed for the recommended duration, or at all. The study found that participants breastfed fully for fewer than four months on average.

There are many reasons why women do not breastfeed. Some cannot do it due to existing health conditions; others stop earlier than planned because of work schedules and inadequate support.

In such cases, infant formula, usually based on cows' milk, is the only recommended alternative to breast milk in the first 12 months of life.

As with any observational study, the authors caution that further research is needed to understand the mechanisms behind the association.