Professor Barry Everitt, Cambridge University
We are talking about the science of addiction. Weíre joined in the studio by Professor Barry Everitt, whoís Professor of Behavioural Neuroscience here at Cambridge University. Good evening, how are you doing?
Barry - Fine, thank you!
Kat - Excellent, now weíre gonna start by talking about Ė what is addiction? What does it mean when we talk about someone who is addicted to something?
Barry - Well, I think the easiest way to think about an individual who is addicted is someone who compulsively uses drugs, seeks and uses drugs at the expense of other activities and finds it impossible to relinquish that drug-seeking/drug-taking habit. The essence of addiction is compulsive or out of control use which really differentiates it from the kind of drug-taking that many people do at some point in their lives where they take drugs like cigarettes. Itís easy to think about cigarettes or alcohol: you smoke and you may drink to experience the effects of the compounds in tobacco smoke and alcohol itself. Having done that, some individuals are vulnerable to these effects and they go on to keep using and using. They lose control over that use and gradually progress to the stage where it becomes addiction.
Kat - Whatís going on in the brain when someone, say, is becoming an addict to drugs or alcohol Ė what sort of changes are going on there?
Barry - Very complex changes. For many years research in this area has focussed on what might be the mechanism that mediates the effects of drugs and itís in this context that a particular chemical messenger in the brain, dopamine, has been implicated. It seems that many drugs from different classes: nicotine, cocaine, heroine, alcohol Ė all individually different drugs Ė all have this ability to increase dopamine in particular parts of the brain. This may be a key element of why the drugs are initially positive in terms of their effects. That doesnít explain the progression to a more compulsive form of drug use. This really moves beyond the realms of a simple chemical messenger system to encompass adaptation to the chronic taking of the drug in many parts of the brain.
Kat - Why can one person have a drink and itís fine and someone else will become an alcoholic if itís all the same systems?
Barry - Thatís the key question. We tend to talk about vulnerability. Vulnerability is undoubtedly in part genetically determined. Thereís been some progression in understanding in what vulnerability means.
Kat - So are we talking about an addictive personality?
Barry - Yes, but not in the sense that addicts are simply born and not made. This isnít a single gene type of disorder. Itís a behavioural trait thatís under the regulation of many different genes. We know about one of those traits in particular from quite recent research which is that individuals who have an impulsive trait or an impulsive tendency (in other words they respond rather too quickly and without sampling the environment) tend, if theyíre given exposure to drugs, not simply to take them more readily but to escalate their intake. Having escalated their intake, they then undergo a series of adaptations to the brain which sees them progress into compulsive use so that they canít stop.
Kat - So thatís the sort of thing. Thereís a slight thing I want to digress on to which is that some people can become addicted to chemical things like drugs and alcohol and some people seem to be addicted to physical behaviours. Chris youíve got some examples:
Chris - Iíve got an email here from Sam Key. He says, ĎIím a high school teacher and music teacher in Brisbane, Australia. I really enjoy listening to the podcast version of the programme whilst Iím having a cup of tea or coffee.í Therein lies the clue, Ďabout a month ago I decided to cut back on my caffeine intake and decided to quit cold turkey. Unfortunately, it was a school day and by lunch time I had a splitting headache and was very moody. My students asked me why I was a bit grumpy and they convinced me to have a cup of coffee at lunchtime and to give up coffee during the holidays. Whatís happening to cause this?í
Barry - Well, what happens Ė if youíre going to have an addition this isnít a bad one to have because itís (a) quite trivial and (b) quite easy to relinquish. What happens with people who drink coffee and drink coffee very frequently is that they develop tolerance to the caffeine thatís in the coffee. As they develop tolerance to the caffeine: when the caffeine isnít there they experience discomfort in the form of withdrawal which can be things like a headache and it can be also maybe minor mood changes but sometimes even things like palpitations that come with withdrawal from caffeine. You then take more caffeine and you have to do that more and more frequently until eventually you have a situation where people are drinking vast quantities or coffee and caffeine or tea and caffeine during the day. Then when they suddenly stop and decide to go cold turkey Ė it often happens to people on weekends actually, when they take coffee during the week to stay active at work and then at the weekend they tend to take less. They have headaches and they feel bad. If you just stay with that withdrawal symptom for a couple of days it disappears.
Chris - But not with heroin, presumably?
Barry - Well, with heroin thereís also a physical withdrawal syndrome which, a major theory of addiction says, individuals will take heroin not so much to get the positive effects of the drug but to stop feeling so bad when youíre in a state of withdrawal. But thatís neither necessary nor sufficient to explain the compulsive use of heroin and many addicts will use heroin over a long period of time without ever undergoing withdrawal. Withdrawal illness is not a necessary and sufficient condition for addiction.
Kat - And very briefly, what about people who can get addicted to physical behaviours and these kinds of things? We had someone who says they think theyíre addicted to internet porn. Is that the same kind of mechanism thatís going on as well?
Barry - Well, who knows whether there are any mechanisms that are the same that are going on? I think to some extent there is an issue of semantics here. Maybe itís easier to think in terms again of compulsive use: that individuals may engage in behaviours that they find difficult to relinquish. You could describe that as being addicted. I would prefer to say that they were compulsive visitors to internet porn sites and were doing that rather than undergoing some state or withdrawal or whatever, if they didnít have access.
Chris - Barry, why has the brain got a system in it that lets us get addicted to things? It seems like itís such a bad thing to have because weíve outlined a few bad examples. Why should we have that wiring?
Barry - It isnít there so that you can get addicted. Itís presumably there because you need a mechanism in the brain that mediates the positive effects of natural goals and rewards like food and drink and social rewards and effective systems. Like any system in the brain it consists of groups of neurones in the brain that talk to each other and they have chemical messengers. The chemical messengers in this system happen to be ones that are potently affected by drugs that are taken. So you get a kind of a superhit on the chemical systems which is probably, at least early on, a part of the mechanism that causes you to seek that hit again and again.