Scientists Edge Closer to Understanding How Ketamine Can Treat Depression

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Scientists have investigated why ketamine appears to treat depression. Getty Images

Over the past few years, the party drug and animal tranquilizer ketamine has emerged as a fast-acting treatment for depression. Now, a study on mice has shed light on the brain mechanisms that could make the drug so potent in treating the mood disorder.

More than 300 million people live with depression—whose symptoms include a persistently low mood and loss of interest in activities that were once enjoyed—but experts aren't sure about what causes it.

Depression is generally treated through cognitive behavioral therapy or antidepressant medications, such as selective serotonin reuptake inhibitors (SSRIs). In recent years, scientists have explored whether ketamine could be another weapon in the arsenal at a doctor's disposal. Last month, the U.S. Food and Drug Administration approved a nasal spray to treat depression that contained esketamine, a drug similar to ketamine.

In this new study, published in the journal Science, researchers simulated a condition similar to depression by injecting mice with a stress hormone. Tests revealed the hormone lowered the number of outgrowths known as dendritic spines on neurons, or nerve cells, in the prefrontal cortex, a part of the brain that plays a key role in decision making. ​The team found ketamine restored the spines and appeared to reverse the behavior of the mice.

James Stone, a clinical senior lecturer in the department of neuroimaging at King's College London told Newsweek: "The study builds on previous work that shows that ketamine can restore dendritic spines in depression. The unique aspect of this paper is the demonstration that the change in dendritic spine formation is associated with measurable changes in connectivity between neurons.

"This [the study] gives one possible biological mechanism which may underlie the clinical picture of depression," said Stone. "Only by testing other drugs with this experiment will we know the effect that they have on dendritic spine formation."

Last year, a separate study suggested ketamine worked against depression by tapping into the brain's opioid system. That hit back at previous studies, which suggested ketamine tackled depression by blocking the glutamate receptor NDMA.

The research comes amid what is known as the psychedelic renaissance, which has seen scientists investigate whether psychoactive drugs such as MDMA and LSD could be used to treat mental illnesses such as depression, anxiety and PTSD. Such studies are conducted in a safe laboratory environment, and scientists do not recommend self-medicating with illegal drugs.

We are still far from moving away from ditching SSRIs, Stone said.

"It is too soon to say whether MDMA or LSD are effective antidepressants. SSRIs have been demonstrated to be effective against the clinical symptoms of depression, and have also been shown to increase dendritic spine density in previous studies, and so it is unlikely we will be moving away from their use at any time in the foreseeable future."