Why do only some people get addicted?

We posed Layne's question to Dr Amy Milton at Cambridge University. Amy - Many people use drugs of abuse and never become addicted. So, alcohol is a really good example. Most people will go down to the pub, have a few drinks after work and is not ever a problem for them. But there are certain populations of people, people who have vulnerabilities.

If you are someone who's quite anxious, you're probably not going to enjoy using some types of drugs like for instance cocaine, which makes people quite paranoid and anxious if they take a lot of it. However, you might find that drugs like alcohol help to relieve some of their anxiety and so, you will be perhaps more likely to become addicted to those drugs.

There are some vulnerabilities like in alcoholism we're very highly heritable. So for instance, if you have particular genes that mean you don't really feel the effects of a hangover, that means in the early stages of use, you can drink more because you're not having the awful hangovers afterwards and that escalation in use then makes you more likely to become addicted.

Hannah - Thanks, Amy. And so, what proportion of the population suffer from problems with addiction?

Amy - It's perhaps surprisingly low for the numbers you would expect. So, of the people who abuse cocaine for instance, actually, only 20% of those individuals are classified as being addicted. It seems that the majority can actually have control over their drug use which, if you think again of the case of alcoholism, it's sort of a common sense example, most people can control their alcohol intake but there's a subpopulation of people who then find that they're not able to control their use. But obviously, because alcohol is a legal drug, more people use it in the first place which means the absolute numbers are greater than you would see for that subpopulation who become addicted to class A drugs for instance.