Grey matter levels linked with smoking uptake

A new study by university researchers in Cambridge, Warwick and Fudan in China has found that levels of grey matter in the brain’s frontal lobe - where we make decisions and decide whether or not to follow rules - is linked to an individual’s likelihood of taking up smoking during adolescence. Professor Trevor Robbins is from Cambridge University’s department of psychology and is the study’s co-author. He’s been telling me all about it…

Trevor - The adolescent brain is in a very plastic and developing stage. It's very vulnerable to nicotine and its effects. And so if you start smoking, then the chances are that you will continue smoking as an adult. So what we did was to rely on this fantastic horizon study with European labs, where we screened 2000 14 year olds. We measured their behaviour and their attitudes, including their smoking behaviour and their attitudes to that. And also we scan their brains, not only at 14, but also follow ups at 19 and 23. And one of the main findings of the paper is that for those adolescents who were smoking at 19, already by age 14 there was a change in their brain.

克里斯- And critically, Trevor, you are saying that at 14 they weren't smoking yet?

Trevor - Exactly. They weren't smoking yet, but they came to smoke after 14. But at age 14 they had a loss of grey matter in the frontal lobes, which are those structures just beyond the eyes in the brain. Grey matter being nerve cells. And that occurred before smoking. The degree of loss of the grey matter correlated with how much later they became smoking, as it were.

克里斯- What does that bit of the brain do, do we think? And can we square that with why this might be happening?

Trevor - Yes, we can. That's a really key question. So what we did in this study is we gave a number of questionnaires, and one of the questionnaires was actually about rule breaking. Do you have a tendency to break rules to be unconventional and not do the norm and maybe disobey your parents or your teachers or whatever. Those questions correlated with the loss of grey matter in the left frontal lobes. Now, there has been a report in the literature about this in brain damaged patients who have damage to the left frontal lobe, they have a problem with rule breaking. So we found results which agreed with that earlier study and provides us with a behavioural mechanism for understanding why they may be smoking earlier. Because maybe they're just going against what their parents and teachers say.

克里斯- Are the changes focused just in that part of the brain or do you see changes elsewhere? Because, of course, different areas of the brain are all talking to each other, they're connected, and so therefore what happens in one place does influence elsewhere as well. So do you see any knock on or secondary changes?

特雷弗-这是一个非常好的问题。所以第一个point to make is that the left frontal cortex is quite a large area. There are different bits of it, which probably have different functions, but among those functions, adhering to rules may very well be one of them. It's also true that these parts of the brain are connected to other regions of the brain, which we know are involved in addiction. So a very important connection is to the structure called the stratum, where dopamine has an important role in reward and so-called reinforcement mechanisms, which are a very important part of addiction and how drugs manipulate systems to produce addiction. The fact that nicotine is working on the adolescent developing brain probably is another very important factor.

克里斯- It sounds then from what you're saying like there's a sort of one two punch going on where we have a predilection to break rules and therefore render one susceptible behaviourally to trying a tobacco or nicotine laced product in the first place - and that could be cigarettes or vaping, presumably, in this era - and then there's a secondary effect, which is that the nicotine itself then almost reinforces the situation because the brain is vulnerable to and susceptible to the effects of nicotine that then entrenches this.

Trevor - Absolutely Chris. And actually there is a second part of the story, which is interesting, and it's this, that the left frontal lobes may be involved in initiation, but once you've started smoking, it seems that the more you smoke, then the more there's an effect on the right frontal lobes. And the right frontal lobes are involved in the enjoyment aspects of sensation seeking. So they're probably involved in controlling the circuits, which depend on dopamine, which nicotine works on initially to produce the hit. And so the second part of this story is the development of nicotine addiction, the reinforcement of the maintenance of smoking, which may depend on nicotine itself or something to do with smoking having some toxic effect on the right frontal lobes and actually reducing grey matter there as well.

克里斯- Understanding these mechanisms is obviously rewarding and fulfilling because it explains a lot. But does it have any application in terms of, we know that smoking is a problem, numbers have been going down, but they've since gone up a bit, especially with vaping again, and we're worried about that. So understanding this now, does this give us any kind of tool with which to try and tackle the problem?

Trevor - You've raised a very important issue. Education has to figure strongly. We have to be able to say that there are some individuals, maybe we can identify them, who we have to counsel very carefully and say, now, look, we are really serious about this. You really are at risk here. And maybe that will have an influence. We all know that that's a problem; telling adolescents what to do doesn't always work.