The importance of low IQ to early diagnosis of autism.

This study followed 8,000 young children from 2 months to nearly 6 years old to understand the role of IQ in autism. Researchers found that children later diagnosed with autism consistently had lower IQ scores compared to other children, even from very early ages. Lower IQ was linked to more severe autism symptoms. This is the first study to show that lower IQ appears before autism diagnosis and may be an early sign of autism.

This large-scale prospective study of 8,000 US children aged 2-68 months examined the relationship between early IQ and autism diagnosis. The research included over 15,000 assessments with autism outcomes determined by 2-4 years of age. Results consistently showed significantly lower IQ scores in children with ASD compared to typically developing children across all age groups. Lower IQ was associated with greater autism severity as measured by ADOS Calibrated Severity Scores.

Notably, verbal IQ was no better than full-scale IQ for predicting ASD cases. This represents the first prospective study establishing low early IQ as a major feature of ASD in early childhood, suggesting atypical brain circuitry affecting both verbal and nonverbal abilities precedes autism diagnosis.

Early IQ assessment may serve as an important component of autism screening and diagnostic processes. Lower IQ scores in young children could prompt earlier autism evaluation and intervention. The findings suggest that cognitive assessment should be integrated into early autism identification protocols, potentially leading to earlier diagnosis and support services.

The abstract does not specify study methodology, control group characteristics, or demographic details of the sample. The population is described as representative of NIH-funded research participants, which may limit generalizability. No information provided about potential confounding factors or assessment tools used for IQ measurement.

Some individuals can flexibly adapt to life's changing demands while others, in particular those with Autism Spectrum Disorder (ASD), find it challenging. The origin of early individual differences in cognitive abilities, the putative tools with which to navigate novel information in life, including in infants later diagnosed with ASD remains unexplored. Moreover, the role of intelligence quotient (IQ) vis-à-vis core features of autism remains debated. We systematically investigate the contribution of early IQ in future autism outcomes in an extremely large, population-based study of 8000 newborns, infants, and toddlers from the US between 2 and 68 months with over 15,000 cross-sectional and longitudinal assessments, and for whom autism outcomes are ascertained or ruled out by about 2-4 years.

This population is representative of subjects involved in the National Institutes of Health (NIH)-funded research, mainly on atypical development, in the US. Analyses using predetermined age bins showed that IQ scores are consistently lower in ASD relative to typically developing (TD) children at all ages (p < 0.001), and IQ significantly correlates with social, non-social, and total Calibrated Severity Scores (CSS) on the Autism Diagnostic Observation Schedule (ADOS) (p<0.01). Lower IQ is associated with greater autistic impairments. Note, verbal IQ (VIQ) is no better than the full-scale IQ to predict ASD cases.

These findings raise new, compelling questions about potential atypical brain circuitry affecting performance in both verbal and nonverbal abilities and preceding an ASD diagnosis. This study is the first to establish prospectively that low early IQ is a major feature of ASD in early childhood. LAY SUMMARY: The role of IQ scores in autism remains debated. We systematically investigate the contribution of early IQ in an extremely large study of 8,000 children between 2 and 68 months with autism outcomes by about 2-4 years.

We show that IQ scores are consistently lower in ASD relative to TD children. This study is the first to establish prospectively that low early IQ is a predictor for ASD diagnosis in early childhood.