‘Smart genes’ in a drop of blood can predict how clever you are

Test for intelligence could be developed that uses only a person’s DNA, say US and British scientists

INTELLIGENCE could be measured with a swab of saliva, or a drop of blood, after scientists showed for the first time that a person’s IQ can be predicted just by studying their DNA.

In the largest study looking at the genetic basis for intelligence, researchers at the University of Edinburgh and Harvard University have discovered hundreds of new genes linked to brain power.

Previous studies have suggested that around 50 per cent of intelligence is inherited, and the rest comes through upbringing, friendship groups and education. That figure was calculated by studying identical twins who share the same DNA, therefore any differences in IQ between them must be non-genetic.

But nobody knew which were the “smart genes”. Now by studying the genetic data from more than 240,000 people, scientists have found 538 genes which are linked to intelligence.

Researchers were able to predict intelligence solely based on a person’s DNA, a breakthrough which could potentially help doctors to diagnose impaired cognitive ability, or allow children to be given a tailor-made education based on their innate abilities.

Dr David Hill, of the University of Edinburgh’s Centre for Cognitive Ageing and Cognitive Epidemiology, who led the research, said: “Our study identified a large number of genes linked to intelligence.

“We were also able to predict intelligence in another group using only their DNA.”

The study also showed that the same genes which influence intelligence are also linked to other biological processes such as length of life.

Although it is known that intelligent people live longer, it was generally assumed that the link was due to social causes, such as a better education, leading to a more well-paid job, which brings a higher standard of living and a healthier life.

The new research suggests that intelligent people are biologically fitter.

The team also found that genes linked with problem-solving powers were associated with the process by which neurons carry signals from one place to another in the brain.

“We have shown that two biological processes, neurogenesis, the process by which new brain cells are created, and myelination of the central nervous system, are associated with intelligence differences,” said Dr Hill.

“And some of the genetic variants that are linked with an increase in intelligence are also linked with an increase in life expectancy.”

Professor Ian Deary, the study’s principal investigator , from the University of Edinburgh’s Centre for Cognitive Ageing and Cognitive Epidemiology, said: “We know that environments and genes both contribute to the differences we observe in intelligence.

“This study adds to what we know about which genes influence intelligence, and suggests that health and intelligence are related in part because some of the same genes influence them.”

The study used data from the UK Biobank, a major genetic study into the role of nature and nurture in health and disease.

Previous studies by King’s College London discovered that up to 65 per cent of the difference in pupils’ GCSE grades was down to genetics, after analysing genetic data from 12,500 twins.

The findings of the latest research were published in the journal Molecular Psychiatry.