Methods: From six research centres in four European countries we recruited 437 children and adults with ASD and 300 controls between the ages of 6 and 30 years with IQs varying between 50 and 148. We conducted in-depth clinical phenotyping including IQ and a wide range of observational, interview and questionnaire measures of the ASD phenotype, as well as co-occurring psychiatric symptoms. We examined whether there are sex, age, and IQ differences in the severity of ASD symptoms and co-occurring psychiatric symptoms.
Results: The cohort showed heterogeneity in ASD symptom presentation, with only minimal to moderate site differences on core clinical and cognitive measures. On both interview and observational measures, ASD symptom severity was lower in adults compared to children and adolescents. The precise pattern of differences varied across measures but there was some evidence of both lower social symptoms and lower repetitive behaviour severity in adults. Males had higher ASD symptom scores than females on clinician-rated but not on parent-reported dimensional measures of ASD symptoms. In contrast, self-reported ASD symptom severity was higher in adults compared to adolescents, and in females than males (in adults only). Scores on ASD symptom measures were moderately negatively associated with IQ. Males with ASD had higher levels of Inattentive ADHD symptoms than females and both Inattentive and Hyperactive/Impulsive ADHD symptoms were lower in adults than children and adolescents.
Conclusions: The well-established phenotypic heterogeneity in ASD is well captured in the LEAP cohort. Variation both in core ASD symptom severity and in commonly co-occurring psychiatric symptoms were systematically associated with sex, age, IQ – and whether clinician, parent or self-reported. The accelerated longitudinal design of the LEAP cohort will enable us to track trajectories of the ASD phenotype and co-occurring conditions over development and relate these to the wide range of candidate biomarkers also tested in the sample.
|Number of pages||21|
|Early online date||23 Jun 2017|
|Publication status||E-pub ahead of print - 23 Jun 2017|
- autism spectrum disorder