Scientists in China are conducting a world-first clinical trial of deep brain stimulation (DBS) on drug addicts, in the hope that the technology will extinguish addiction, quite literally, with the flip of a switch.

Key points: Shanghai conducts first clinical trial of deep brain stimulation for meth addiction

Shanghai conducts first clinical trial of deep brain stimulation for meth addiction Previous brain lesioning surgeries left patients with mood disorders and lost memories

Previous brain lesioning surgeries left patients with mood disorders and lost memories Doctors can make patients feel agitated or cheerful remotely with a tweak of the settings

The technique, which has long been used for movement disorders like Parkinson's disease, involves drilling two small holes into a patient's skull and feeding electrodes deep into their brain.

A device that acts as a kind of pacemaker for the brain is implanted and used to electrically stimulate targeted areas.

The first clinical trial of DBS for methamphetamine addiction is being conducted at Shanghai's Ruijin Hospital, along with parallel trials for opioid addicts.

Doctors also want to use the experimental brain surgery to treat a range of other psychiatric conditions, including anorexia and Tourette syndrome. ( AP: Erika Kinetz )

Scientists in Europe have struggled to recruit patients for their DBS addiction studies, and complex ethical, social and scientific questions have made it hard to push forward with this kind of work in the United States, where the devices can cost US$100,000 ($140,000) to implant.

China — which has a long and troubled history of brain surgery on drug addicts — is emerging as a hub for this kind of research.

Punitive anti-drug laws can force addicts into years of compulsory treatment, including "rehabilitation" through labour.

The country now has a large patient population, government funding and ambitious medical device companies ready to pay for DBS research.

'Magical' machine controls emotions

A brain scan of a methamphetamine addict showing electrodes implanted to stimulate an area of the brain associated with addiction. ( AP: Erika Kinetz )

The first patient in China to undergo experimental DBS surgery for methamphetamine addiction, who gave his name only as Yan, became addicted to meth after the birth of his son in 2011.

Every time Mr Yan smoked the drug, he gambled. He estimated he lost around $150,000. His wife divorced him. He rarely saw his son.

Mr Yan checked into a hospital for detox, moved to a new town to escape bad influences and took Chinese traditional medicine. But he relapsed every time.

"My willpower is weak," he said. He chose brain surgery.

Risks included dying of a brain haemorrhage or emerging with seizures, an infection or changes to his personality. And in the end, he may go right back on drugs.

The surgeon, Dr Li Dianyou, drilled through Mr Yan's skull and threaded two electrodes down to his nucleus accumbens, a small structure near the base of the forebrain that has been implicated in addiction.

Later that day, he went under general anaesthesia for a second surgery to implant a battery pack in his chest to power the electrodes in his skull.

As the electrodes activated in Mr Yan's brain, he felt a surge of excitement.

Dr Li used a tablet computer to remotely adjust the machine thrumming inside Mr Yan's head, making the patient feel agitated or cheerful with a tweak of the settings.

"This machine is pretty magical. He adjusts it to make you happy and you're happy, to make you nervous and you're nervous," Mr Yan said.

More than six months later, he said he's still off drugs.

Dr Li Dianyou uses a tablet computer to adjust the settings of a deep brain stimulation device implanted in Mr Yan's brain. ( AP: Erika Kinetz )

Murky ethics of brain surgery

Before there were brain implants in China, there was brain lesioning.

Desperate families of heroin addicts paid thousands of dollars for unproven and risky surgeries in which doctors destroyed small clumps of brain tissue.

Brain lesioning quickly became profitable at some hospitals, but it left a trail of patients with mood disorders, lost memories and altered sex drives.

DBS builds on that history. But unlike lesioning, which irreversibly kills brain cells, the devices allow brain interventions that are — in theory — reversible.

The technology has opened a fresh field of human experimentation globally.

Western attempts to push forward with human trials of DBS for drug addiction have foundered, even as China has emerged as a hub for this kind of research. ( AP: Erika Kinetz )

"As doctors, we always need to think about the patients," said Dr Sun Bomin, director of Ruijin Hospital's functional neurosurgery department.

"They are human beings. You cannot say, 'Oh, we do not have any help, any treatment for you guys'."

Dr Sun has tried to turn Ruijin into a centre of DBS research, not just for addiction, but also Tourette syndrome, depression and anorexia.

Some critics believe this surgery should not be allowed, arguing that such human experiments are premature and will not address the complex biological, social and psychological factors that drive addiction.

Scientists don't fully understand how DBS works and there is still debate about where electrodes should be placed.

There is also scepticism in the global scientific community about the general quality and ethical rigour — particularly around issues like informed consent — of clinical trials done in China.

"It would be fantastic if there were something where we could flip a switch, but it's probably fanciful at this stage," said Adrian Carter, who heads the neuroscience and society group at Monash University in Melbourne.

There are eight registered DBS clinical trials for drug addiction being conducted in the world, according to a US National Institutes of Health database. Six are in China.

But the suffering wrought by the opioid epidemic may be changing the risk-reward calculus for doctors and regulators in the United States: In February, the US Food and Drug Administration greenlighted a clinical trial in West Virginia of DBS for opioid addicts.

AP