This study used the Norwegian Mother, Father and Child Cohort Study to look at mother and child pairs. Researchers checked the mother's diet around week 22 of pregnancy and the child's diet at age 3. A parent reported the child's ADHD symptoms at age 8, and ADHD diagnoses came from a national patient registry. About 77,768 pairs were included in the diagnosis analyses and 37,787 in the symptom analyses.
When mothers ate a higher quality diet during pregnancy, their children had slightly fewer reported ADHD symptoms at age 8 (a change of -0.28 per one step up in the diet score). These children also had a lower chance of an ADHD diagnosis (relative risk 0.87). When mothers ate more ultra-processed food, children had slightly more symptoms (+0.25), but there was no clear change in diagnosis risk. The child's own diet at age 3 showed no reliable link to either outcome.
The authors call these effects small and see no clinical meaning for generally healthy families whose diets are, on average, adequate, though they note small effects can still matter across a whole population. The study is observational, and the authors say no cause and effect should be read into it.
Source: Borge T, Biele G, Papadopoulou E, et al.. The associations between maternal and child diet quality and child ADHD – findings from a large Norwegian pregnancy cohort study. BMC Psychiatry (2021). doi:10.1186/s12888-021-03130-4