Scientists have identified hundreds of new genes associated with intelligence, a joint research project from the University of Queensland's Brain Institute and its partners in the Netherlands revealed on Tuesday.

As well as the 939 new "smart genes," the authors said in another study that they had identified over 500 genes associated with neuroticism, an important risk factor for depression and schizophrenia.

"These results are a major step forward in understanding the neurobiology of cognitive function as well as genetically related neurological and psychiatric disorders," the study said.

More than 250,000 individuals were tested for their genetic data and measurements of intelligence, while the study into neuroticism took data from almost half a million respondents.

Together these studies provide new insights into the neurobiology and genetics of cognition.

According to researchers, the findings suggest that our brains have distinct genetic gene clusters responsible for the effects of depression and worry.

Scientists also believe the newly-found "smart genes" may help protect against Alzheimer's disease and conditions like Attention Deficit Hyperactivity Disorder (ADHD).