Infant muscle tone and childhood autistic traits: A longitudinal study in the general population.

Autistic trait data were available for 2905 of 4055 children. Compared with children excluded, included children had higher mean IQ (103.1 vs 96.4), were more often Dutch (61.2% vs 34.0%), and had mothers with lower mean psychopathology scores (0.24 vs 0.37), though muscle tone scores were similar (1.92 vs 1.96). The outcome measures were parent-reported questionnaires, and the study did not perform the Autism Diagnostic Observation Schedule, which the paper calls the gold standard for formal ASD evaluation. Neuromotor reliability was modest to substantial, with reported ICCs of 0.52 for short-interval test-retest and 0.64 for interobserver assessment. Only 30 children (0.9%) had confirmed autism diagnoses, so the direct ASD diagnosis analysis was underpowered and not significant. The authors state that clinical implications of the modest effect sizes should be considered with caution. The study did not know whether any child received intervention for neuromotor delays. It was a general population cohort, not a clinic-referred sample of children already diagnosed with autism.

The supplied conflict statement says only that, for the other authors, no competing financial interest exists.

Do not conclude that low infant muscle tone causes autism or can diagnose autism. The study found a modest prospective link with parent-reported autistic traits, and the analysis of confirmed autism diagnoses was not significant because only 30 children had confirmed diagnoses.