China has gene-edited cloned monkeys to show symptoms of mental illness including schizophrenia and depression.

The five macaques were born after cells were cloned then embryos were edited to remove the BMAL1 gene.

This led to them displaying the mental illness traits brought on by disrupting their circadian rhythms, a study in the National Science Review revealed.

They were edited with the same tool - CRISPR/Cas 9 - used by Chinese scientist He Jiankui, who controversially claimed to have created the world's first genetically edited human babies recently.

Unlike Mr He's experiment, the Chinese government authorised and funded the monkey trial, carried out by researchers at the country's Institute of Neuroscience.


Researcher Chang Hung-Chun said the findings could help develop treatments for human medical conditions ranging from diabetes and sleep disorders to neurodegenerative diseases and cancer.

Only China has the technology to clone captivity-bred primates, with the first born at the beginning of 2018 using the same technique that produced Dolly the sheep.

However, the latest study has raised further questions over the ethics of using a species so similar to humans for such invasive research.

Alan Bates, an Oxford Centre for Animal Ethics fellow, said the fact the study was on mental illness was "especially controversial".

If monkeys' mental processes were "sufficiently close to humans to provide a valid model, then it would certainly be unethical to experiment on them", he said.

He added that he could not see how laboratory-reared animals "could fail to show symptoms akin to mental illness".

Image: He Jiankui said he created the first gene-edited baby in 2018

Andrew Knight, a professor of animal welfare and ethics at the University of Winchester, said the study was "disturbing" and "very irresponsible".

"Human mental illnesses are complex, and even harder to predict than purely physical diseases," he told South China Morning Post.

"The likely benefit from harming animals in this way is extremely small.

"However, there is no doubt that these animals will suffer - and probably, very significantly.

"Primates are highly intelligent and social animals. It is not ethical to deliberately harm them, and especially when the chance of tangible benefit for human patients is so small. Such research is very irresponsible."

Arthur Caplan, professor bioethics at New York University, is split on the study, saying the low success rates of cloning carried an "ethical price" because there is a chance of malformed animals.

However, he said that if scientists are "competent" it is ethical to study human diseases on gene-edited animals that you "could not ethically try first in humans".