Developmental language disorder - a comprehensive study of more than 46,000 individuals.

Developmental language disorder (DLD) is characterized by enduring low language abilities with a significant functional impact, in the absence of biomedical conditions in which language impairment is part of a complex of impairments. There is a lack of awareness of DLD even among healthcare professionals. Here we estimated the prevalence of DLD and its links to reading and learning difficulties and physical and mental health in the Danish Blood Donor Study (N = 46,547), where DLD-related information is based on questionnaires (self-report). We compared the questionnaire-derived DLD status with the relevant language-related diagnoses from hospital registers. We also investigated the genetic architecture of DLD in a subset of the cohort (N = 18,380). DLD was significantly associated with reading and learning difficulties and poorer mental and physical health. DLD prevalence was 3.36%-3.70% based on questionnaires, compared with 0.04% in hospital registers. Our genetic analyses identified one genome-wide significant locus, but not a significant heritability estimate. Our study shows that DLD has health-related implications that may last into adulthood, and that DLD may be undiagnosed in general healthcare. Furthermore, DLD is likely more genetically heterogeneous than narrower developmental language phenotypes. Our results emphasize the need to raise awareness of DLD and consider criteria for molecular studies of DLD to reduce case heterogeneity.

Mental states and activities in Danish narratives: children with autism and children with language impairment.

This study focuses on the relationship between content elements and mental-state language in narratives from twenty-seven children with autism (ASD), twelve children with language impairment (LI), and thirty typically developing children (TD). The groups did not differ on chronological age (10;6-14;0) and non-verbal cognitive skills, and the groups with ASD and TD did not differ on language measures. The children with ASD and LI had fewer content elements of the storyline than the TD children. Compared with the TD children, the children with ASD used fewer subordinate clauses about the characters' thoughts, and preferred talking about mental states as reported speech, especially in the form of direct speech. The children with LI did not differ from the TD children on these measures. The results are discussed in the context of difficulties with socio-cognition in children with ASD and of language difficulties in children with LI.