Researchers have identified over 1,016 specific genes associated with intelligence, the vast majority of which are unknown to science.
An international team conducted a large-scale genetic association study of intelligence and discovered 190 new genomic loci and 939 new genes linked with intelligence, significantly expanding our understanding of the genetic bases of cognitive function.
Led by statistical geneticist Danielle Posthuma from Vrije Universiteit Amsterdam in the Netherlands, the researchers performed a genome-wide association study (GWAS) of almost 270,000 people from 14 independent cohorts of European ancestry.
All these people took part in neurocognitive tests that measured their intelligence, and when researchers contrast their scores with variations in the participants' DNA – called single nucleotide polymorphisms (SNPs) – you can see which mutations are associated with high intelligence.
From over 9 million mutations detected in the sample, Posthuma's team identified 205 regions in DNA code linked with intelligence (only 15 of which had been isolated before), and 1,016 specific genes (77 of which had already been discovered).
According to the team, the genes that make for smartness also look to confer a protective effect to overall cognitive health, with the analysis finding a negative correlation with Alzheimer's disease, attention deficit/hyperactivity disorder, depressive symptoms, and schizophrenia.
The intelligence genes were however correlated with increased instances of autism, and also longevity, suggesting people with these genetic underpinnings of high intelligence are more likely to live longer.
"Our results indicate overlap in the genetic processes involved in both cognitive functioning and neurological and psychiatric traits and provide suggestive evidence of causal associations that may drive these correlations," the researchers write.
"These results are important for understanding the biological underpinnings of cognitive functioning and contribute to understanding of related neurological and psychiatric disorders."
The work builds upon similar research led by Posthuma and published last year. That time, though, the researchers only identified 40 new genes linked to intelligence, so this year's analysis represents a much greater haul unlocking considerably broader genetic bases for intelligence.
And it's not just our understanding of intelligence that's getting blown wide open.
In a separate new study also led by Posthuma, researchers conducted another large GWAS – this time involving 449,484 individuals – and identified 136 genome-wide significant loci associated with neuroticism, and 599 implicated genes.
Of the genetic loci, 124 were new to science, and given that so far, through GWAS researchers had only identified 16 loci associated with neuroticism, it's a big step forward for our understanding of what helps power conditions such as depression, anxiety, and schizophrenia.
According to the team, there are two distinct genetic 'subclusters' of neuroticism – one relating to 'depressed affect', and the other to worry.
While it may take some time before the full implications of this can be understood, the team says we now have "new leads and testable functional hypotheses for unraveling the neurobiology of neuroticism", which may go a long way to helping people who experience neuroticism in the future.
The findings are reported in Nature Genetics here and here.