Previous research has shown that associative conditioning, also known as Pavlovian-type learning, is an efficient way to train the brain to subconsciously associate one stimuli with another. A recent study conducted at the Weizmann Institute of Science has revealed that exposing smokers to rotten fish or eggs in their sleep could help reduce the amount of cigarettes they smoke in a day even if they don’t remember smelling cigarette smoke and a foul odor in their sleep.

“We have not yet invented a way to quit smoking as you sleep,” lead researcher Dr. Anat Arzi said in a statement. “That will require a different kind of study altogether. What we have shown is that conditioning can take place during sleep, and this conditioning can lead to real behavioral changes. Our sense of smell may be an entryway to our sleeping brain that may, in the future, help us to change addictive or harmful behavior."

Arzi and her colleagues recruited 66 smokers who were interested in quitting smoking but had not explored other avenues to achieve it. Participants were asked to complete a questionnaire regarding their smoking habit before they were split into different groups. The first group was monitored during a night of sleep and exposed to a combination of cigarette smoke and a foul odor throughout the night. The second group was exposed to the same smell combination but while they were awake.

While smokers who stayed awake while being exposed to cigarette smoke and a foul odor did not smoke fewer cigarettes following the experiment, smokers who were asleep when they were exposed to the paired smells smoked significantly fewer cigarettes over the course of the next week. Smokers who were exposed to the paired smells during stage 2, non-REM sleep — the stage of sleeping associated with “memory consolidation” — smoked an average of 30 percent fewer cigarettes.

According to the Centers for Disease Control and Prevention, around 68.8 percent of U.S. adult cigarette smokers report they want to quit smoking. Smokers who quit early enough can lower their risk for heart disease, stroke, chronic obstructive pulmonary disease (COPD), lung cancer, and other types of cancer. Current smoking cessation techniques include clinical interventions, telephone counseling, behavioral therapy, nicotine replacement products, and prescription non-nicotine medications.

Source: Sobel N, Harel, Eshel N, Samnon P, Holtzman Y, Arzi A. Olfactory Aversive Conditioning during Sleep Reduces Cigarette-Smoking Behavior. The Journal of Neuroscience. 2014.