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'Extinction therapy' could help smokers kick habit, study suggests

'Extinction therapy' could help smokers kick habit, study suggests. Science & Technology World Website

It sounds like torment for the smoker attempting to quit: handling packets of cigarettes and watching footage of people smoking, without being allowed to light up.

However, scientists believe that lengthy exposure to environmental triggers for cravings could be precisely what smokers need to help them quit. The technique, known as extinction therapy, targets the harmful Pavlovian associations that drive addiction with the aim of rapidly “unlearning” them.

The latest study, by scientists at the Medical University of South Carolina, found that after two one-hour sessions people smoked significantly fewer cigarettes one month after treatment compared to a control group.

The study was not an unqualified success – many participants still relapsed after treatment – but the authors believe the work could pave the way for new approaches to treating addiction.

Michael Saladin, the psychologist who led the work, said: “When I initially saw the results from this study it was pretty eye-opening.”

In smokers, environmental triggers have typically been reinforced thousands of times so that the sight of a lighter, for instance, becomes inextricably linked to the rush of nicotine that the brain has learned will shortly follow.

After quitting an addictive substance, these associations fade slowly over time, but people often flounder in the first days and weeks when cravings are most powerful.

Saladin and others believe it is possible to fast-track this process in carefully designed training sessions, to help people over the initial hurdle.

“The [therapy] is designed to literally update the content of the memory,” he said.

When we access memories, scientists have discovered, the memory is temporarily destabilised before being reconsolidated and returned to long-term storage. This makes human memory fallible in everyday life, but could also represent a window of clinical opportunity to tamper with the unhelpful memories that underpin addiction.

In the latest study, published in Jama Psychiatry, 44 participants were initially shown a brief clip of people smoking, intended to activate and destabilise the smoking-related memory. Ten minutes later (thought to be the optimal time interval for manipulating the memory) the participants began an hour-long exposure session in which they were repeatedly shown pictures and videos of people smoking and given cigarettes to play with.

A control group of 44 smokers were given the same hour-long exposure session, but without the initial smoking memory trigger – instead, they were shown a video clip of people washing dishes. Both group had two sessions on consecutive days.

After a month, the treatment group were smoking significantly fewer cigarettes on average each day (seven, compared to 10 for the control group). However, the treatment group did not have lower urine levels of cotinine (a proxy for nicotine intake) and did not manage to stay off cigarettes completely for significantly longer, leading some to express scepticism about the technique’s promise.

Professor Robert West, an expert in smoking cessation at University College London, said: “You’re dealing with really heavily over-learned cues. Short-circuiting the extinction process is a tough thing to do and pragmatically it might be very difficult.”

He suggested that prescription medication, which blocks nicotine in the brain, achieves the same objectives far more reliably. The medication has a 30-40% quit rate at six months.

“By far the single most effective thing a smoker can do is to go to the GP and get Chantix [a trade name for the prescription medication varenicline],” said West.

Others were impressed by the findings. Ravi Das, a psychologist at University College London, who is trialling extinction training to reduce alcohol intake in heavy drinkers, said: “It’s a really important study because it’s the first to show an actual effect in real smokers. This is a really exciting way of potentially targeting the mechanisms that lie at the heart of addictive behaviours.”



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