«These results are very exciting as they provide very robust associations with intelligence. The genes we detect are involved in the regulation of cell development, and are specifically important in synapse formation, axon guidance and neuronal differentiation. These findings for the first time provide clear clues towards the underlying biological mechanisms of intelligence», says Danielle Posthuma, Principal Investigator of the study.
The study also showed that the genetic influences on intelligence are highly correlated with genetic influences on educational attainment, and also, albeit less strongly, with smoking cessation, intracranial volume, head circumference in infancy, autism spectrum disorder and height. Inverse genetic correlations were reported with Alzheimer’s disease, depressive symptoms, smoking history, schizophrenia,
Future studies will need to clarify the exact role of these genes in intelligence in order to obtain a more complete picture of how genetic differences lead to differences in intelligence. NeuroscienceNews.com image is for illustrative purposes only.
«These genetic correlations shed light on common biological pathways for intelligence and other traits. Seven genes for intelligence are also associated with schizophrenia; nine genes also with body mass index, and four genes were also associated with obesity. These three traits show a negative correlation with intelligence», says Suzanne Sniekers, first author of the study and postdoc in the lab of Posthuma. «So, a variant of gene with a positive effect on intelligence, has a negative effect on schizophrenia, body mass index or obesity.»
Future studies will need to clarify the exact role of these genes in intelligence in order to obtain a more complete picture of how genetic differences lead to differences in intelligence. «The current genetic results explain up to 5% of the total variance in intelligence. Although this is quite a large amount of variance for a trait as intelligence, there is still a long road to go: given the high heritability of intelligence, many more genetic effects are expected to be important, and these can only be detected in even larger samples», says Danielle Posthuma.