Is intelligence written in the genes?

The evidence keeps piling up.  Many genes are now known to be involved, which reinforces my view that high IQ is just one aspect of general biological good functioning

A gene which may make people more intelligent has been discovered by scientists.  Researchers have found that teenagers who had a highly functioning NPTN gene performed better in intelligence tests.

It is thought the NPTN gene indirectly affects how the brain cells communicate and may control the formation of the cerebral cortex, the outermost layer of the human brain, also known as ‘grey matter.’  Previously it has been shown that grey matter plays a key role in memory, attention, perceptual awareness, thought and language.

Studies have also proved that the thickness of the cerebral cortex correlates with intellectual ability. However, until now no genes had been identified.

Teens with an underperforming NPTN gene did less well in intelligence tests.

Dr Sylvane Desrivières, from King’s College London’s Institute of Psychiatry and lead author of the study, said: “We wanted to find out how structural differences in the brain relate to differences in intellectual ability.

“It’s important to point out that intelligence is influenced by many genetic and environmental factors. “The gene we identified only explains a tiny proportion of the differences in intellectual ability.”

An international team of scientists, led by King’s, analysed DNA samples and MRI scans from 1,583 healthy 14 year old teenagers.

The teenagers also underwent a series of tests to determine their verbal and non-verbal intelligence.

The researchers looked at over 54,000 genetic variants possibly involved in brain development.

They found that, on average, teenagers carrying a particular gene variant had a thinner cortex in the left cerebral hemisphere, particularly in the frontal and temporal lobes, and performed less well on tests for intellectual ability.

The genetic variation affects the expression of the NPTN gene, which encodes a protein acting at neuronal synapses and therefore affects how brain cells communicate.

Their findings suggest that some differences in intellectual abilities can result from the decreased function of the NPTN gene in particular regions of the left brain hemisphere.

Although the genetic variation identified in this study only accounts for an estimated 0.5 per cent of the total variation in intelligence.

However, the findings may have important implications for the understanding of biological mechanisms underlying several psychiatric disorders, such as schizophrenia, autism, where impaired cognitive ability is a key feature of the disorder.

The study was published in Molecular Psychiatry

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