New Zealand scientists said Thursday they had made a breakthrough in understanding depression that could lead to fast-acting medications to treat the illness.
Auckland University research into the action of the drug ketamine on the brain had revealed neural pathways using magnetoencephalography (MEG), which measured the brain's magnetic fields.
"Our interest is in the mechanism of action that ketamine used to be active in the human brain. That will give us a target for other compounds," researcher Dr Suresh Muthukumaraswamy said in a statement.
"It's important as a mechanism to identify potential biomarkers of antidepressant activity in human patients, but for other reasons, we cannot use it for treatment," he said.
"We know that ketamine is active in the frontoparietal circuit of the brain and disconnects these two parts," he said.
"In depression those two parts of the brain work overtime in an over-connected way. It may be that ketamine works as an antidepressant by disconnecting those two parts of the brain and stopping that over-connectivity."
Unlike other anti-depressants, ketamine was very fast acting, but other clinical trials had found the ketamine-induced anti- depression effect only lasted a week or so.
Ketamine, which was developed in the 1960s, was off-patent now and was primarily used as an anaesthetic and sometimes for chronic pain.
"Ketamine's anti-depressant properties were discovered relatively recently and did well in clinical trials. Unfortunately, ketamine is also a drug of abuse, as it's mildly hallucinogenic and it is unclear if it could be used in routine clinical practice, " said Muthukumaraswamy.