The researchers, led by Philipp Khaitovich of the Max-Planck-Institute for Evolutionary Anthropology and the Shanghai branch of the Chinese Academy of Sciences, examined the brains of humans with and without schizophrenia and compared them with chimpanzee and rhesus macaque brains.

Khaitovich said the scientists searched for differences in metabolite concentrations and the expression of genetic instructions in order to identify "molecular mechanisms involved in the evolution of human cognitive abilities."

He said they found the genes and metabolites altered in schizophrenia, especially those related to energy metabolism, are those that rapidly changed during evolution.

"Our new research suggests schizophrenia is a by-product of the increased metabolic demands brought about during human brain evolution. Our brains are unique among all species in their enormous metabolic demand. If we can explain how our brains sustain such a tremendous metabolic flow, we will have a much better chance to understand how the brain works and why it sometimes breaks," he added.

The study appears in the journal Genome Biology.