San Diego scientists say they have found new evidence to support the idea that a common drug — which some users take illegally for its dissociative effects — could be used to treat depression.
Ketamine has long been used as an anesthetic, and some users take it as a hallucinogenic club drug. But a number of studies have shown it may also alleviate depression.
In a new analysis published Wednesday in the journal Scientific Reports, UC San Diego researchers said millions of FDA side effect records reveal that people who took ketamine for pain relief reported lower rates of depression.
"The occurrence of complaints about depression dropped in half after ketamine administration," said UC San Diego Skaggs School of Pharmacy professor Ruben Abagyan, who led the study.
The researchers focussed on the FDA's Adverse Effect Reporting System, a database that tracks negative side effects among people who take various drugs. But the researchers were not primarily interested in bad outcomes.
Instead, they looked for a positive outcome: declining rates of depression among people taking drugs not typically thought of as antidepressants.
They found signs that other common drugs — including Botox, a pain reliever called diclofenac and the antibiotic minocycline — also reduced depression among patients in the FDA database.
Large-scale clinical trials have not yet been carried out to test the safety and effectiveness of ketamine as an antidepressant.
Abagyan said the drug's reputation could be one of the reasons it has not been more thoroughly tested. And because ketamine is already so widely available in standard medical practice, Abagyan said drug companies do not have a strong profit motive to pay for expensive human trials.
The UC San Diego researchers said their population-scale analysis is not a substitute for directly testing the drugs in large numbers of patients. But it does bolster the findings of smaller human studies that show ketamine and other drugs can potentially help clear up depression.
"They definitely have a statistically significant antidepressant effect," Abagyan said. "This study basically is an additional justification for a proper clinical trial."
Scientists who have studied ketamine's potential as an antidepressant, but who were not involved in this study, emailed KPBS their thoughts about the research.
University of Miami psychiatry professor Charles Nemeroff wrote that the study was, "very interesting."
"The findings are of considerable interest. However the interpretation of the findings are key," he wrote, saying it will be important to understand whether ketamine is directly treating depression or simply relieving pain, which can indirectly help people experience less depression.
The UC San Diego researchers said they controlled for this variable by comparing people who took ketamine with those who took other pain medications. They said they still found a larger drop in depression among those who took ketamine.
UC San Diego professor emeritus David Feifel, who has used ketamine to treat depressed patients, wrote that the evidence for ketamine's antidepressant effects is already strong.
"I think the authors produced an interesting analysis although I don't think this retrospective, correlational analysis will add much to the current evidence supporting ketamine's antidepressant properties," he wrote.
