Researchers from Amsterdam UMC and the Wellcome Sanger Institute greatly expanded a genetic study of intelligence by making use of information from people who never completed an intelligence test. This allowed them to conduct the largest genetic study of its kind to date, involving nearly half a million people of European ancestry. The study is published in Nature Genetics.
UK Biobank is a large research study containing health and genetic information from around half a million people in the UK. Around 40% of its participants never completed the problem-solving test used in this study. The researchers used other information about these participants, including health, behaviour and socioeconomic measures, to estimate their likely test scores. Combining these estimates with actual test scores increased the sample from around 270,000 to more than 455,000 people. David van den Berg, Amsterdam UMC: “The challenge was making sure the estimated scores still captured intelligence, rather than simply reflecting the other information we used to calculate them. We tested that extensively.”
People who completed the test tended to be more highly educated than those who did not, meaning that previous studies were based on a somewhat selective group. Daniel Malawsky, Wellcome Sanger Institute: “Who takes part in a test can make a real difference to the results. By including information from people who did not take the test, we could get a broader picture of the genetics of intelligence.”
The larger study revealed much more about the genetics of intelligence. It identified about 40% more small differences in our DNA code linked to intelligence. These common differences each tend to have only a very small effect. The larger group also made it easier to find rare differences in our DNA code, which can have much larger effects. The rare differences pointed to 26 genes linked to lower intelligence scores, compared with only five when the researchers used measured test scores alone. Fourteen of these 26 genes are already known to cause neurodevelopmental conditions, while eight had no strong previous evidence linking them to intelligence or neurodevelopmental conditions.
Intelligence is related to many important outcomes in modern societies. Understanding its genetics could therefore help researchers understand not only the biology of neurodevelopmental conditions, but also why people differ in important life outcomes. Abdel Abdellaoui, Amsterdam UMC: “Modern societies have become increasingly complex to navigate, and intelligence is a trait that is strongly rewarded. It is closely related to education, income and health, so understanding why people differ in intelligence can also help us understand social inequality.”
The results also show that the effects of DNA differences can vary considerably from person to person. Hilary Martin, Wellcome Sanger Institute: “The link with neurodevelopment is particularly interesting. Some of the same rare genetic differences that contribute to neurodevelopmental disorders also seem to influence intelligence more broadly, even in people without a diagnosis.”
Article link
Read the full article in Nature Genetics
General lay summary and frequently asked questions
Background and answers to frequently asked questions, written by the research team.
Contact
Dr Abdel Abdellaoui
Department of Psychiatry, Amsterdam UMC, University of Amsterdam
Amsterdam Neuroscience
Email: a.abdellaoui@amsterdamumc.nl