Reproductive fitness and genetic risk of psychiatric disorders in the general population.
Level 3 - non-randomized controlled study
Population-based observational cohort study
PubMed 28607503 · doi:10.1038/ncomms15833
What was done
The authors analyzed genomic data from 150,656 Icelanders, excluding individuals diagnosed with schizophrenia, autism, bipolar disorder, major depression, or attention deficit hyperactivity disorder (ADHD). They evaluated selection pressures on sequence variants and rare copy-number variants predisposing to these psychiatric disorders by examining their association with reproductive fitness metrics, specifically the number of children and age at first child.
What was found
In unaffected individuals, higher polygenic risk of autism was associated with fewer children and older age at first child, whereas higher polygenic risk of ADHD was associated with having more children. No evidence was found for a selective advantage from high polygenic risk of schizophrenia or bipolar disorder. Rare copy-number variants conferring moderate-to-high risk of psychiatric illness were associated with having fewer children and showed stronger negative selection pressure than common sequence variants. Specific effect sizes, confidence intervals, and p-values were not provided in the abstract.
Why it matters
This study provides empirical population genomic evidence addressing the evolutionary paradox of how psychiatric risk alleles persist despite reduced fitness, showing divergent selection dynamics across disorder-specific polygenic risk profiles.
Limits
The abstract reports directional associations without quantitative effect sizes, statistical test statistics, or confidence intervals. The study population was restricted to Iceland, which may limit generalizability to other demographic and genetic backgrounds. Individuals diagnosed with the disorders were excluded, focusing only on the unaffected general population.
Cited by
- supports Autism spectrum disorder (ASD) traits and associated genetic variants are associated with significantly lower fertility.