Genetic and phenotypic heterogeneity in early neurodevelopmental traits in the Norwegian Mother, Father and Child Cohort Study.

The study used registry data for diagnoses, which means it could not distinguish between co-occurring diagnoses and substitution diagnoses, nor could it confirm the exact timing of all diagnoses relative to the age 3 assessment. The genetic analyses were limited to participants of European ancestry, which restricts the generalizability of the genetic findings to other populations. The exploratory nature of the factor analysis in a large sample may have led to some overfitting, so the identified factors should not be interpreted as definitive distinct entities. The study did not include measures of cognitive ability or tics, limiting the scope of the traits analyzed. Many items in the questionnaires were from screening tools designed for clinical populations, and their validity in a general population sample, particularly for children under 4, has mixed evidence.

The study was supported by Helse Sør-Øst RHF, Norges Forskningsråd, Simons Foundation Autism Research Initiative, and the Norwegian Institute of Public Health (FHI).

Do not interpret the associations between early traits and later diagnoses as evidence that a specific early behavior predicts a specific condition. The study found that early social and communication difficulties were associated with almost all neurodevelopmental diagnoses, indicating these traits are non-specific markers of developmental risk rather than diagnostic criteria.