Schizophrenia has long been documented to have existed among humans throughout recorded history, and now researchers are saying that the condition only emerged when humans diverged from Neanderthals.
For a study published in the journal Biological Psychiatry, Ole Andreassen and colleagues compared genetic information from Neanderthals and modern humans and found an association between markers of human evolution and genetic risk for schizophrenia. Based on their findings, the researchers suggest that schizophrenia did not exist in early hominids.
It is still not clear what exactly causes the condition but researchers know that genetics has a significant role in schizophrenia development. According to Andreassen, the study's senior author, some think of schizophrenia as a "side effect" arising from advantageous variants in genes that are related to the development of human traits, such as cognitive and language skills, that may have increased risks for developing psychoses.
Neanderthals were used as a point of comparison for the study because they are the closest relatives of the early humans. When examining the Neanderthal genome, the researchers looked for specific regions that could give insight into which point in evolutionary history schizophrenia developed.
During their study, the researchers found that certain genome regions underwent positive selection around the time humans diverged from Neanderthals. Additionally, these regions were likely to contain parts of the human genome that have been associated with schizophrenia.
"Our findings suggest that schizophrenia vulnerability rose after the divergence of modern humans from Neanderthals," said Andreassen, adding that the results of their study support the hypothesis that schizophrenia is a by-product of human brain evolution.
There is no cure for schizophrenia at the moment, so treatment options available are geared toward managing and reducing symptoms instead of completely reversing them.
However, a study published in the journal Psychology Medicine in May showed that the brains of those who have the condition actually attempt self-repair in an effort to fight schizophrenia.
The condition has been linked to widespread reduction in the brain's tissue volume but it was observed that certain brain regions show a subtle increase in tissue over time.
According to Lena Palaniyappan and colleagues, regardless of the kind of tissue damage initially recorded, the brains of schizophrenic patients were shown to be constantly attempting to reorganize themselves. This hints at the brains' effort not just to limit damage but even fight off the condition as well.
These findings are important because they show that it is possible for the brain to repair itself. This may then be used in developing treatments targeted to support the brain's efforts at reversing the effects of schizophrenia.
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