There is also evidence that scores on tests of nonverbal ability of children with DLD decrease over the course of development.DLD is associated with an elevated risk of social, emotional and mental health concerns. For instance, in a UK survey, 64% of a sample of 11-year-olds with DLD scored above a clinical threshold on a questionnaire for psychiatric difficulties, and 36% were regularly bullied, compared with 12% of comparison children. In the longer-term, studies of adult outcomes of children with DLD have found elevated rates of unemployment, social isolation and psychiatric disorder among those with early comprehension difficulties. However, better outcomes are found for children who have milder difficulties and do not require special educational provision. Prevalence
Epidemiological surveys in the US and the UK converge in estimating the prevalence of DLD in five-year-olds at around 7%. Therefore, the prevalence is about one in every 15 children. By these statistics, in a classroom of 30 students, 2 would have DLD. In research by Tomblin et al., prevalence of DLD in racial/ethnic groups was highest in Native Americans, with African Americans being the next highest, followed by Hispanic people, and then White people. No students of Asian descent presented with DLD; however, other research does indicate that DLD is present in children of Asian descent. Research
Much research has focused on trying to identify what makes language learning difficult for some children.
However, subsequent studies have found that, though DLD runs in families, it is not usually caused by a mutation in FOXP2 or another specific gene. Current evidence suggests that there are many different genes that can influence language learning, and DLD results when a child inherits a particularly detrimental combination of risk factors, each of which may have only a small effect. Nevertheless, study of the mode of action of the FOXP2 gene has helped identify other common genetic variants involved in the same neural pathways that may play a part in causing DLD.Language disorders are associated with aspects of home environment, and it is often assumed that this is a causal link, with poor language stimulation leading to weak language skills. Twin studies, however, show that two children in the same home environment can have very different language outcomes, suggesting we should consider other explanations for the link. Children with DLD often grow up into adults who have relatively low educational attainments, and their children may share a genetic risk for language disorder.One non-genetic factor that is known to have a specific impact on language development is being a younger sibling in a large family. Associated factors
It has long been noted that males are more affected by DLD than females, with a sex ratio of affected males-to-females around 3 or 4:1. However, the sex difference is much less striking in epidemiological samples, suggesting that similar problems may exist in females but are less likely to be detected.