Five-year predictive validity of DSM-IV conduct disorder research diagnosis in 4(1/2)-5-year-old children

OBJECTIVE

This longitudinal study of a non-referred, population-based sample tested the 5-year predictive validity of the DSM-IV conduct disorder (CD) research diagnosis in children 4(1/2)-5 years of age.

METHOD

In the E-Risk Study, a representative birth cohort of 2,232 children, mothers were interviewed and teachers completed mailed questionnaires to assess children's past 6-month CD symptoms. A follow-up assessment was conducted when children were 10 years old.

RESULTS

CD-diagnosed 5-year-olds were significantly more likely than controls to have behavioural and educational difficulties at age 10. Increased risk for age-10 educational difficulties persisted after controlling for age-5 IQ and ADHD diagnosis. Although the majority of CD-diagnosed 5-year-olds had no CD symptoms at age 10, findings suggest that these "remitted" children continued to experience behavioural and educational problems 5 years later despite their apparent remission from CD.

CONCLUSIONS

DSM-IV CD symptoms validly identify preschool-aged children who continue to have behavioural and educational problems in middle-childhood.

Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism

Children's intellectual development is influenced by both genetic inheritance and environmental experiences. Breastfeeding is one of the earliest such postnatal experiences. Breastfed children attain higher IQ scores than children not fed breast milk, presumably because of the fatty acids uniquely available in breast milk. Here we show that the association between breastfeeding and IQ is moderated by a genetic variant in FADS2, a gene involved in the genetic control of fatty acid pathways. We confirmed this gene-environment interaction in two birth cohorts, and we ruled out alternative explanations of the finding involving gene-exposure correlation, intrauterine growth, social class, and maternal cognitive ability, as well as maternal genotype effects on breastfeeding and breast milk. The finding shows that environmental exposures can be used to uncover novel candidate genes in complex phenotypes. It also shows that genes may work via the environment to shape the IQ, helping to close the nature versus nurture debate.