Dutch researchers uncovered 1,016 genes that they associated with intelligence, 939 of which are completely new to science. The findings help to identify the biological underpinnings of cognitive functions, but also those of related neurological and psychiatric disorders.
The team, led by Danielle Posthuma, a statistical geneticist at the Vrije Universiteit Amsterdam in the Netherlands, performed a genome-wide association study (GWAS) of almost 270,000 individuals. In such studies, scientists analyzed a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait. Generally, GWASs look for associations between single-nucleotide polymorphisms (SNPs) and traits like major human diseases, but can equally be applied to any other organism.
Each person took neurocognitive tests that gauged their level of intelligence, whose scores were then paired with variations in DNA — the SNPs. This is a straightforward method for identifying which mutations are associated with high intelligence.
Of the over 9 million mutations that were detected in this huge sample, the researchers found 205 regions in DNA linked with intelligence, 190 of which were new to science, as well as 1,016 specific genes, of which only 77 had been previously discovered. The mutations that were linked with high intelligence seem to protect overall cognitive health, with people carrying these mutations being less likely to develop Alzheimer’s, ADHD, depressive symptoms, and schizophrenia. On the downside, high intelligence mutations were linked to a higher incidence of autism. People with high intelligence were also likely to live longer, the team reported in Nature.
Previously, Posthuma and colleagues identified 40 new genes linked to intelligence in a cohort of about 80,000 people. This time, they certainly outdid themselves.
The study used a novel statistical method called MAGMA to pinpoint specific types of cells and tissue where the genes were expressed. Many of the genes were expressed in a region of the brain called the basal ganglia, a cluster of neurons known to be involved in learning, cognition, and emotion. This suggests parts of this brain region are worth targetting with new pharmaceutical drugs in order to prevent or treat some psychiatric disorders.
In a separate study, also published in the journal Nature, the researchers identified nearly 500 genes and 124 loci (regions in DNA) associated with neurotic traits by combing through databases of 449,400 individuals from the UK Biobank and 23andMe. Neurotic traits include anxiety and depression.
This study suggests that people who worry a lot inherited different genes than those who more likely to be depressed, which suggests there are different genetic pathways that underlie these behaviors.
Both studies are remarkable in that they provide new leads for unraveling the neurobiology of neuroticism but also serious psychiatric diseases.