The study in question involved 90 participants around the age of 28, who drank more than the recommended amount of alcohol in the U.K., where the study was conducted, but hadn’t been diagnosed with a disorder. The men drank at least 40 units per week in mostly beer and the women 30, and were therefore at risk of developing alcohol use disorder.
The research was carried out over three days, with around ten days between the first and last sessions. On the first and last days, researchers asked the participants about their attitudes toward drinking. They were also given a 150ml glass of beer, which they could drink after rating a series of images shown on a screen. The volunteers looked at photos of beer, wine, and soft drinks including orange juice. They rated how pleasant the drinks looked, as well as their urge to drink the beer in front of them and how much they would enjoy it. A message then flashed on the screen prompting the volunteers to drink the beer at their own pace, and consider how much they enjoyed it and their desire to drink more.
In a second experiment conducted around 48 hours after the first, the participants were shown images of beer and non-alcoholic drinks. Volunteers were either presented with a glass of beer or juice, and asked to rate their urge to drink what was shown in the pictures. The screen prompted the subjects to drink their beer or juice. But this time they were unexpectedly told to stop, and the drink taken away. The team hoped this would destabilize what are known as maladaptive reward memories related to drinking.
After what the team described as the memory reactivation process, they either injected participants with ketamine—a substance used by vets to anesthetized animals and also as an illegal party drug—or a placebo for 30 minutes. A third group received ketamine without memory reactivation, to control for any effects of ketamine itself. Ketamine is thought to interfere with reactivated memories, study co-author Ravi Das of the UCL Clinical Psychopharmacology Unit told Newsweek.
The researchers found a big drop in drinking levels in the group who had their memories disrupted and took ketamine, by about 23.5 units per week and a fall in the number of days they drank. The volunteers also reported having less of an urge to drink, and enjoying alcohol less. This effect lingered for nine months.
Typically, people who have treatment for heavy drinking rebound over time and treatment can take weeks or months, Das explained. “However, over the 9-month period that we followed up participants, they did not rebound to their former drinking levels. Given that the entire experimental ‘intervention’ was a one-off session that lasted around an hour, this level of effect was pretty striking,” he argued.
Detailing what led the team to carry out the study, Das continued: “We were interested to see whether ketamine could weaken drinking-related reward memories when given following a procedure that was intended to make those memories unstable.”
“Previous experimental research has shown that reward memories can be destabilized by briefly presenting ‘cues’ related to the memory. In this case, the ‘cues’ we used were images of beer, pictures of people drinking and interiors of bars; all things that people would associate with drinking beer.”
If validated in clinical trials, ketamine could be used to treat alcohol and drug disorders “however this is still likely to be several years in the future,” said Das.
He went on to stress readers should not try to replicate the findings themselves.
“This is still an experimental intervention and all procedures were conducted by experienced researchers under full medical supervision,” said Das. “There are many subtle nuances to memory reactivation and drug dosing that would make it very unlikely that the same effects would be seen with street ketamine.”
Celia Morgan, a professor of psychopharmacology at the University of Exeter who did not work on the paper, told Newsweek: “The study is important as it is the first to show in human drinkers that memories can be modified in this way and that real-world drinking can be reduced.”
She said the takeaway is “that you can modify your own memories, they aren’t fixed but are being updated all the time, which has implications for a great number of areas of life.”
“What is surprising is that the memory retrieval procedure (showing someone a beer in a lab and then telling them they can’t drink it) for such a short duration has impacts on actual alcohol drinking. While the ketamine alone reduces drinking, this is enhanced when combined with this memory procedure.”
Pointing out a limitation, Morgan said: “Whilst in animals you can easily see these memory processes working it is much harder in humans to tell as we aren’t able to inspect the cells in the brain, more work is needed to find out doses, mechanisms and try and ascertain that this really is consolidation.”
But Morgan said ketamine has the potential to be used as a treatment not just for alcohol but all addictions.
Matt Field, professor of psychology at the University of Sheffield, commented in a statement: “These are promising findings but the strong claim that ketamine and MRM [maladaptive reward memories] leads to ‘unprecedented’ long-lasting reductions in alcohol consumption are not justified on the basis of this data.
“Further investigation with a larger sample size and preregistration of methods and hypotheses before data collection begins is needed to support this claim.”
