A new study has mapped the effects of ketamine on the brain, finding that repeated use over extended periods creates widespread structural changes in the brain’s dopamine system.

The study found that repeated ketamine exposure leads to a decrease in dopamine neurons in midbrain regions linked to regulating mood. They also revealed an increase in dopamine neurons in the hypothalamus, which regulates the body’s basic functions like metabolism and homeostasis.

A former finding that ketamine decreases dopamine in the midbrain, may indicate why long-term abuse of ketamine could cause users to exhibit similar symptoms to people with schizophrenia. 

The researchers suggest that their new finding that ketamine increases dopamine in the parts of the brain that regulate metabolism, published in Cell Reports, may help explain why it shows promise in treating eating disorders.

They suggest this strengthens the case for developing ketamine therapies that target specific areas of the brain, rather than administering doses that wash the entire brain in ketamine.

Raju Tomer, the senior author of the paper, stated: “Instead of bathing the entire brain in ketamine, as most therapies now do, our whole-brain mapping data indicates that a safer approach would be to target specific parts of the brain with it, so as to minimise unintended effects on other dopamine regions of the brain.”

Tracking detailed data

The researchers tracked highly detailed data that enabled them to track how ketamine affects dopamine networks across the brain. 

The insight revealed that ketamine reduced the density of dopamine axons (nerve fibers) in the areas of the brain responsible for hearing and vision, while increasing dopamine axons in the brain’s cognitive centers, which may help explain the dissociative behavioral effects observed in individuals exposed to ketamine.

Malika Datta, a co-author of the paper, added: “The restructuring of the brain’s dopamine system that we see after repeated ketamine use may be linked to cognitive behavioral changes over time.”

Most studies of ketamine’s effects on the brain to-date have looked at the effects of acute exposure – how one dose affects the brain in the immediate term. 

For this study, researchers examined repeated daily exposure over the course of up to ten days. Statistically significant alterations to the brain’s dopamine makeup were only measurably detectable after ten days of daily ketamine use. 

The researchers also assessed the effects of repeated exposure to the drug at two doses, one dose analogous to the dose used to model depression treatment in mice, and another closer to the dose that induces anesthesia. The drug’s effects on dopamine system were visible at both doses.

“The study is charting a new technological frontier in how to conduct high-resolution studies of the entire brain,” said Yannan Chen, paper co-author. 

It is the first successful attempt to map changes induced by chronic ketamine exposure at what is known as “sub-cellular resolution,” in other words, down to the level of seeing ketamine’s effects on parts of individual cells.

Most sub-cellular studies of ketamine’s effects conducted to date have been hypothesis-driven investigations of one area of the brain that researchers have targeted because they believed that it might play an important role in how the brain metabolises the drug. 

This study is the first sub-cellular study to examine the entire brain without first forming such a hypothesis.

Bradley Miller, a Columbia psychiatrist and neuroscientist who focuses on depression, said: “Ketamine rapidly resolves depression in many patients with treatment-resistant depression, and it is being investigated for longer-term use to prevent the relapse of depression. 

“This study reveals how ketamine rewires the brain with repeated use. This is an essential step for developing targeted treatments that effectively treat depression without some of the unwanted side effects of ketamine.”

“This study gives us a deeper brain-wide perspective of how ketamine functions that we hope will contribute to improved uses of this highly promising drug in various clinical settings as well as help minimise its recreational abuse. More broadly, the study demonstrates that the same type of neurons located in different brain regions can be affected differently by the same drug,” added Tomer.

Mindbloom has launched its new Mastermind Series of psychedelic programmes for overcoming heartbreak, burnout and other unique mental health challenges. 

Led by and developed with leading experts in the field, each programme combines specialised teachings with ketamine therapy.

All programmes will include six ketamine therapy sessions focusing on a specific mental health issue, expert-led audio, video, and written content for preparation, treatment, and integration, practical tools such as meditation, one-on-one coaching and group integration sessions.

The first programme in the Series is ‘Recovering from Rejection and Failure’, led by Dr Guy Winch who is a leading authority on emotional health, and a best-selling author and TED speaker whose talks have received over 30 million views.

Winch’s programme focuses on healing and preventing emotional injuries that people suffer in their personal, professional and romantic lives.

Mindbloom CEO and Founder Dylan Beynon stated: “More than 100 studies and 20 plus years of clinical use show that ketamine therapy may be the most transformational mental health treatment available today.

“In the face of epidemics of mental illness, addiction, and loneliness, we’re thrilled to offer our clients access to top experts across a range of issues – and to pair their expertise with our best-in-class ketamine therapy honed over hundreds of thousands of treatment sessions.”

“Emotional wounds like rejection and failure can be even more devastating than physical wounds, yet we don’t give them the same time and attention,” added Dr Winch.

“I’m thrilled to combine my techniques for emotional first aid with ketamine therapy, which has been shown to increase neuroplasticity and help build emotional resilience.”

Additional Mastermind programmes will be released in the coming months, including: Getting Unstuck, by Dr Elizabeth Lombardo; Beating Burnout, by Dr Shauna Shapiro; and Coping with Cravings, by Dr Jud Brewer

“Americans are struggling with heartbreak, burnout, and other challenges every day, and they’re looking for new tools to address them,” said Mindbloom’s Medical Director Dr Leonardo Vando.

“I’m grateful to these experts for providing Mindbloom’s clients with the unique practices and insights they’ve cultivated during their distinguished careers, to help them overcome the biggest obstacles in their lives.”

Cybin has announced positive Phase 2 topline safety and efficacy data for its proprietary deuterated psilocybin analogue – CYB003 – for the treatment of major depressive disorder (MDD).

Results from Cybin’s study have shown that 79% of patients were in remission from depression at six weeks after receiving two doses of CYB003.

CYB003 demonstrated a large improvement in symptoms after one dose and a total of 79% of patients were responsive to the treatment. The compound also demonstrated an excellent safety profile in doses tested, with all reported adverse events mild to moderate and self–limiting.

Additionally, Cybin has stated that the magnitude of improvement was superior compared to approved antidepressants and recently reported data with other psychedelics, stating that the effects translate into an unprecedented effect size.

The company has said that the results compare favorably to pooled data from 232 industry studies of current standard-of-care antidepressants, SSRIs, submitted to the FDA.

The announcement follows Phase 2 interim results in early November 2023, which demonstrated that CYB003 saw a “rapid, robust and statistically significant reduction in symptoms of depression three weeks following a single 12mg dose compared to placebo”.

Cybin CEO, Doug Drysdale, stated: “We are delighted to share that CYB003 achieved the primary efficacy endpoint in this study and showed rapid and statistically significant improvements in depression symptoms after a single dose, with a clear incremental benefit of a second dose, resulting in four out of five patients in remission from their depression at six weeks.

“This is an impressive finding and follows on from the unprecedented interim results we announced earlier this month.”

Drysdale emphasised that the strength of the data will support CYB003 into Phase 3 of the study.

Cybin CMO, Amir Inamdar, added: “The significant reduction in depression symptoms observed in our Phase 2 study is highly gratifying.

“At the three-week primary efficacy endpoint, a single 12mg dose of CYB003 showed a rapid, robust, and highly statistically significant improvement in depression symptoms compared to placebo, with a -14.08 point difference in change from baseline in MADRS. 

“This translated into a very large effect size. Similar significant and robust effects were also seen with a single 16mg dose, which resulted in an improvement in symptoms of depression as measured using the MADRS total score by about 13 points versus placebo. 

“These effects were evident on day one with the 16mg dose and were also highly statistically significant. When data from 12mg and 16mg are pooled, these robust effects are maintained. Further, with two doses, response and remission rates in excess of 75% were observed with CYB003 (12mg). 

“With these findings in hand, we are encouraged by the potential of CYB003 to help those with MDD and look forward to progressing to a multinational, multisite Phase 3 study early next year.”

Cybin is planning on submitting topline data to the FDA with an aim to hold a Phase 2 meeting in Q1 of 2024, with further 12-week durability data from Phase 2 CYB003 expected in Q1, and recruitment for the Phase 3 study anticipated to begin by the end of Q1 2024.