Prevalence and heritability of parental‐reported speech and/or language difficulties in a Swedish population‐based twin sample
Rebecka Keijser,
Jakob Åsberg Johnels,
Marika Habbe,
Paul Lichtenstein,
Henrik Larsson,
Sebastian Lundström,
Mark J. Taylor,
Kristiina Tammimies
Affiliations
Rebecka Keijser
The Center of Neurodevelopmental Disorders (KIND) Centre for Psychiatry Research Department of Women's and Children's Health Karolinska Institutet and Child and Adolescent Psychiatry Stockholm Health Care Services Stockholm County Council Stockholm Sweden
Jakob Åsberg Johnels
Gillberg Neuropsychiatry Centre Institute of Neuroscience and Physiology University of Gothenburg Gothenburg Sweden
Marika Habbe
The Center of Neurodevelopmental Disorders (KIND) Centre for Psychiatry Research Department of Women's and Children's Health Karolinska Institutet and Child and Adolescent Psychiatry Stockholm Health Care Services Stockholm County Council Stockholm Sweden
Paul Lichtenstein
Department of Medical Epidemiology and Biostatistics Karolinska Institutet Stockholm Sweden
Henrik Larsson
Department of Medical Epidemiology and Biostatistics Karolinska Institutet Stockholm Sweden
Sebastian Lundström
Gillberg Neuropsychiatry Centre Institute of Neuroscience and Physiology University of Gothenburg Gothenburg Sweden
Mark J. Taylor
Department of Medical Epidemiology and Biostatistics Karolinska Institutet Stockholm Sweden
Kristiina Tammimies
The Center of Neurodevelopmental Disorders (KIND) Centre for Psychiatry Research Department of Women's and Children's Health Karolinska Institutet and Child and Adolescent Psychiatry Stockholm Health Care Services Stockholm County Council Stockholm Sweden
Abstract Background Research on genetic and environmental influences on speech and/or language difficulties (SaLD) is sparse, with inconsistent heritability estimates. We aimed to estimate the prevalence of parental reported SaLD and the relative contributions of genetic and environmental factors for the phenotype using a Swedish population‐based twin sample. We hypothesized that there would be a stronger genetic than environmental effect on SaLD. Methods Data were collected from The Child and Adolescent Twin Study in Sweden. The study sample included 16,774 twin pairs (16,946 males, 16,602 females), of which 5141 were monozygotic, 5861 dizygotic (DZ), and 5772 opposite‐sex DZ pairs. The language items in the Autism–Tics, Attention‐Deficit Hyperactivity Disorder, and other Comorbidities inventory were used to categorize individuals as having parental‐reported SaLD. A classical twin design was used to estimate the relative contribution of genetic and environmental factors to the liability of SaLD. Results The prevalence of SaLD was 7.85% (95% confidence interval (CI) [7.57%–8.15%]) and 7.27% (95% CI [6.99%–7.55%]) when excluding individuals with autism and intellectual disability (ID). We also found that SaLD were significantly more prevalent in males than females with a ratio of 2:1. The heritability was estimated to be 75% (95% CI [67%–83%]) for SaLD. Shared environment played a significant role with an estimated contribution of 22% (95% CI [14%–30%]). The heritability estimate was reduced to 70% but with overlapping CI when excluding individuals with autism and ID. Conclusions We provide evidence that SaLD is common in the population and under strong genetic influence. Future studies should focus on mapping the genetic architecture of SaLD and related disorders.
