Measuring subthreshold autistic traits in the general population: Psychometric properties of the Adult Autism Subthreshold Spectrum (AdAS Spectrum) scale

The Adult Autism Subthreshold Spectrum (AdAS Spectrum) has been developed to assess the wide spectrum of autistic-like clinical and non-clinical features in adults. Nevertheless, its psychometric properties have been analyzed only with clinical individuals so far. This study was aimed at investigating the dimensionality, reliability and validity of the AdAS Spectrum on a non-clinical sample. Participants were 395 Spanish undergraduate students (60% males; mean age of 21.1 years, SD = 2.6), who completed the AdAS Spectrum, the Autism-Spectrum Quotient (AQ), and the Empathy Quotient (EQ). A confirmatory factor analysis supported the seven-factor structure of the questionnaire. Internal consistency was excellent for the total score and acceptable for five factors. Test-retest reliability over a 4-week period was good. Higher AdAS Spectrum scores significantly correlated with higher AQ and lower EQ scores, supporting the validity of the scale. Moreover, participants studying Science/Technology programs did significantly differ from students following Social/Humanities degree courses on all the AdAS Spectrum scores. Overall, findings support the psychometric properties of the AdAS in a non-clinical sample. Future research is needed to further examine the factorial structure and the internal consistency of the scale in larger samples of general population.