Over 500 genes linked to intelligence have been identified in the largest study of its kind.

In a bid to discover which genes are associated with intelligence, scientists compared variation in DNA in more than 240,000 people from around the world.

The study sheds a new light on the biological building blocks of people's differences in intelligence.

Researchers from Edinburgh, Southampton and Harvard University identified 538 genes that play a role in intellectual ability and also found 187 regions in the human genome that are linked to thinking skills.

Genes found to be linked to intelligence also appeared to influence other biological processes.

Some genes linked to intellectual ability are associated with living longer, researchers say.

It was 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.

Using these genetic discoveries, scientists next predicted 7% of intelligence differences in an independent group of individuals using their DNA alone.

Dr David Hill from the Edinburgh University said: "Our study identified a large number of genes linked to intelligence.

"Importantly, we were also able to identify some of the biological processes that genetic variation appears to influence to produce such differences in intelligence, and we were also able to predict intelligence in another group using only their DNA."

The study's principal investigator, professor Ian Deary from Edinburgh University, said: "We know that environments and genes both contribute to the differences we observe in people's 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."