Language deficits in specific language impairment, attention deficit/hyperactivity disorder, and autism spectrum disorder: An analysis of polygenic risk.
Ron Nudel, Camilla A J Christiani, Jessica Ohland and 13 others
PMID 31577390WHAT IT FOUND
Genetic risk scores for specific language impairment predicted language difficulties in this sample but did not predict autism or ADHD risk.
This suggests the common genetic variants driving language impairment do not simply add to the risk for autism or ADHD.
Key findings
01Polygenic risk scores derived from specific language impairment studies significantly predicted the narrow language phenotype but not autism spectrum disorder or attention deficit/hyperactivity disorder.
02Children with the narrow language phenotype had significantly higher polygenic risk scores than children with autism spectrum disorder.
03The study used a sample of Danish children selected for having a parent with schizophrenia or bipolar disorder, or as age-matched controls.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was small, with very few cases of narrow language impairment (21), autism (17), and ADHD (46), which reduced the statistical power to detect subtle genetic overlaps. The children were not selected for language problems; they were selected based on parental mental health history, which may affect the generalizability of the findings to the general population. Language assessment relied on a single receptive language test (TROG-2) rather than a comprehensive clinical evaluation including expressive language. The study excluded children with low non-verbal intelligence from the narrow language impairment group, which may limit applicability to patients with co-occurring intellectual disabilities.
Declared interests
The authors declared no conflicting interests, though one author noted acting as a lecturer and scientific counselor to H. Lundbeck A/S. The study was funded by Aarhus Universitet, Lundbeckfonden, and TrygFonden.
The easy way to misread this
Do not interpret the lack of prediction for autism or ADHD as proof that there is no genetic link between these conditions and language impairment. The study only tested common genetic variants using a specific risk score method and had a small sample size, so it cannot rule out other genetic mechanisms or rare variants contributing to shared risks.