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Breaking the habit: Why is it so difficult to change cocaine users’ behaviour?

Dr Karen Ersche at the University of Cambridge has found that people with cocaine addiction are not more likely to alter their behaviour if they know the consequences of their actions. She explains why her findings could be important for how we treat cocaine addiction.

Dr Karen ErscheCocaine addiction can be devastating for individuals and those around them and it is a habit that can be incredibly difficult to break. I wanted to understand why individuals continue taking cocaine even when they understand the negative consequences. Currently there are no medically proven treatments for cocaine addiction and our research has shown us that people addicted to cocaine form habits – including those unrelated to drugs – differently from people who aren’t. Understanding this could help us be more effective in how we treat those with addiction.

We all have our own daily routines and habits that we quickly slip into. They can be good or bad – we might find ourselves taking a drink of water without thinking or biting our fingernails whilst watching the telly. We typically develop them as a result of repetition, and learn to execute them automatically, leaving our brain-power free to concentrate on other things. However, when the situation demands it and our habits are harmful or don’t make sense anymore, we can break them. It requires some effort, but we can do it.

The results from our study suggest that, for people addicted to cocaine, it may not be so easy. Cocaine-addicted people seem to be more prone to developing habits for actions that are rewarded. More importantly, they appear to be more likely to get stuck in these behaviours, even if they know that what they are doing no longer makes sense or even is harmful.

Animal cards used in rewards-based task

In the first task participants learned by trial and error which animal pictures gained them points. The points were later taken away for some of the animal pictures but the people with cocaine addiction tended to continue to answer in the same way. Image source: Science

We trained 125 participants to perform two different tasks – 72 were addicted to cocaine and 53 had no history of drug addiction. In the first task, we asked participants to learn relationships between animal pictures; every time they made a correct response we rewarded them with points. In the second task, they had to learn the relationships between two different pictures that were associated with an electrical shock to either their right or left wrist, and to avoid this shock by pressing the relevant foot pedal.

electric shock

In the second task participants were trained to expect an electric shock to either their left or right wrist when they saw certain pictures. They could prevent the shock by pressing a foot pedal. The participants with cocaine addiction were less likely to develop a habit to avoid the shocks. Image source: Science

As habits generally develop through repetition, we trained all our participants in these tasks over many trials. In the first, reward-based task, the performance of the cocaine-addicted individuals improved over time, whereas in the task in which they had to avoid the electrical shocks, training did not make a difference.

We wanted to find out whether those participants who were addicted to cocaine would change their behaviour, if it no longer gives them the same benefit it once did.

Following this prolonged training period, we then changed the rules and made some of their previously learnt responses meaningless. In the first task, we told participants that some of the animal pictures no longer carried points, and therefore should not be selected in their responses. In the second task, we detached the electrical cable from one of their wrists, so that it would no longer make sense to press the foot pedal to avoid the shock associated with that picture.

We found that people with cocaine addiction formed stronger habits in the points-based task. They were more inclined than the control group to switch to autopilot, and so continued responding in an automatic fashion even when their actions were no longer being rewarded.

However, they were less likely to form a habit to avoid the electrical shocks in the second task. In fact, compared to the control group, they were less likely to attempt to avoid the electrical shocks in the first place.

These findings have significant implications for treating people addicted to cocaine. Interventions that use rewards, in moderation, are more likely to be successful than punitive ones. Training cocaine users to develop more desirable habits to replace drug-taking habits may also be an effective strategy for treatment.

As a psychologist, I am generally interested in understanding what makes us tick. My particular interest in drug addiction is motivated by the opportunity that science offers me to understand behaviours that are damaging to people, and crucially, I want to use this knowledge to develop more effective treatments.

I hope that my work will contribute to improving the lives of people who have been affected by drug addiction and help reduce the widespread stigma attached to them, which may further enhance their chances of recovery.

This work was funded by the Medical Research Council and was conducted at the NIHR Cambridge Biomedical Research Centre and the Behavioural and Clinical Neuroscience Institute and was published today in Science.

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