Lack of evidence for increased genetic loading for autism among families of affected females: a replication from family history data in two large samples.
Girls with ASD do not come from families loaded with more autism genes than boys, so counselors can give equal recurrence figures to all parents.
01Research in Context
What this study did
The team looked at family trees of 1,000+ children with ASD. They counted how many relatives had autism, ADHD, or learning problems. Half of the families had girls with ASD. The other half had only boys with ASD.
They wanted to test the idea that girls need a bigger genetic hit to show autism. If true, families of girls should show more ASD in their relatives.
What they found
Families of girls with ASD did not have more autism than families of boys. Rates of ASD, ADHD, and learning issues were the same in both groups. The data did not support the female protective effect.
How this fits with other research
Ganz et al. (2009) tried a similar two-cohort test with the MET gene. One cohort showed a link to autism, the other did not. Both studies warn that genetic risk markers can look strong in one group and vanish in another.
Wagner et al. (2011) moved the lens from idiopathic families to named syndromes like FXS and CdLS. They showed ASD symptoms cluster differently when a known gene is involved. Heslop et al. (2007) keeps the focus on everyday families, so the papers complement, rather than clash.
Saghazadeh et al. (2017) pooled blood BDNF data across 20 studies. They found a small but real rise in BDNF in ASD. That biomarker work is separate from family history, yet both lines aim to spot who sits in the ASD risk pool.
Why it matters
You can stop telling parents that having a daughter with ASD means the family carries extra genetic burden. The old idea sounded logical, but the numbers do not back it. When you explain recurrence risk to families, use the same figures for boys and girls. This keeps your guidance clear and avoids needless worry.
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02At a glance
03Original abstract
Both the broad and narrow phenotypes of autism have been consistently observed in family members of affected individuals. Additionally, autism spectrum disorders (ASDs) present four times more often in males than in females, for reasons that are currently unknown. In this study, we examined whether there were differences in familial loading of ASD among families of male versus female probands. Analyses were conducted with existing data from two distinct samples. The first sample contained 417 individuals with autism and Asperger's disorder and included information on the ASD diagnoses of their first- and second-degree relatives. The second sample consisted of 405 sibships participating in the Autism Genetic Resource Exchange, of which one or more siblings had an ASD diagnosis. Results from both samples did not suggest significant differences in the prevalence of ASD among relatives of affected males versus females.
Autism : the international journal of research and practice, 2007 · doi:10.1177/1362361307076857