As anyone who has tried to quit smoking will know, it becomes tougher to abstain when you see or smell a cigarette.

Exposing people to these accompanying addition cues without supplying the reward can curb addiction, says a group of researchers in China and the US, but only if memory of the addiction is retrieved first.

Therapists have long known that continually exposing addicted people to cues, such as the smell of a drug, without exposing them to the drug’s effects, can weaken the association between the two. But it is often a short-term fix, and cravings return (Addiction, DOI: 10.1046/j.1360-0443.2002.00014.x).

Research has shown that memories can be changed more permanently if they are retrieved first. It is a bit like opening a document on your computer, making some changes, then resaving it, says David Epstein of the National Institute on Drug Abuse in Bethesda, Maryland.


Extinction training

To see whether this approach could be used as therapy for addiction, Epstein, alongside Yan-Xue Xue of Peking University in Beijing, China, and their colleagues taught hospitalised people in China who were recovering from heroin addiction to retrieve the memory of their addiction by showing them a video involving the drug. The participants were then given one hour of “extinction” training, which involved being exposed to cues such as fake heroin and drug paraphernalia without being given the drug itself.

Participants were asked to rate their craving for heroin before and after exposure to a heroin cue. To provide additional measures of craving, the team monitored the heart rate and blood pressure of the participants before and after cues.

Addicts who had extinction training 10 minutes after memory retrieval showed reduced craving when tested one, 30 and 180 days later. But craving was unaffected for participants who didn’t have their memories retrieved before undergoing extinction training, or who had their extinction training 6 hours after memory retrieval.

From cocaine to stress

The results were similar for heroin- and cocaine-addicted rats that stopped seeking the drug after retrieval and extinction training. The findings are promising, Epstein says, but the team still needs to see how people respond when back in their own home.

“It’s really impressive; an amazing finding,” says Daniela Schiller of Mount Sinai School of Medicine in New York, who studies the use of the same treatment for post-traumatic stress disorder by inducing fear memories in healthy volunteers and then erasing the cues that trigger them.

“This was exactly our hope,” Schiller says, “an experiment that shows that the method does apply to stronger memories and impacts a real life craving.”

Journal reference: Science, DOI: 10.1126/science.1215070