Smoking may cause cognitive functions to decline

I saw an anti-smoking pop-up the other day. I hate pop-ups, pop-unders, pop-throughs and pop-whatever-else-they’ve-come-up-with, but I did appreciate the message. Not enough to make me like pop-ups, but it was nice to know they’re being used for a good purpose, at least. If I remember rightly it mentioned some of the classic health problems associated with smoking, but as usual none of the lesser known ones. For instance, did you know smoking causes stress? That’s one example. Here’s another one. It’s time to dust off your brain trainer, and postpone your application to Who Wants to be a Millionnaire?, because evidence suggests that smoking impairs certain cognitive functions.

There’s some debate in this area though. This is often the case with smoking research. I remember one study that analysed all the evidence on passive smoking, and found that there were no negative health effects – until they removed the studies done by authors connected to the tobacco industry – then it showed, correctly, that there are indeed negative health effects.

In this case, the debate is between some studies that show nicotine improves cognitive functions, and others that say it weakens them. The problem is that many of the studies didn’t include an important ingredient of the scientific process – a control group, in this case, non-smokers. This is important, because without one you couldn’t say whether smoking caused an increase in performance, or removed a deficit. A study in 2000 tried to clear this up. (1)

To measure cognitive function, the researchers used the Sternberg task, which goes a little something like this: a string of letters is presented on a computer screen, then they disappear. Later, a couple of letters come up and you have to say if they were in the original string or not. It’s a test of both memory and reaction time – how long does it take for people to decide whether or not the letters were in the original set, and how accurate are they, under different conditions?

In this study, the ‘conditions’ were whether people were heavy smokers (20+ cigarettes per day), light smokers (10 or fewer cigarettes per day), or non-smokers, and whether they have either recently smoked a cigarette or have abstained for 12 or more hours.

What happened?

When smokers were allowed to smoke, there was no difference in reaction time or accuracy between smokers or non-smokers. The scores were about the same. But, when smokers were deprived of cigarettes for 12 hours before taking the test, the results were different: this time the heavy smokers did worse than the non-smokers. After a cigarette, however, their performance returned to about the same level.

This suggests that smoking does not heighten performance on this task, but merely removes a deficit in performance that smoking itself creates. This is similar to the finding that smoking causes stress.

Urges to smoke

But it raises another question – does nicotine deprivation slow reaction times directly, or is the urge to smoke distracting people from the task?

The technical explanation, some researchers propose, goes like this: drug use is related to an action schema, stored in long-term memory: basically, a set of instructions telling smokers to find and take the drug, which is triggered by a drug-related cue (seeing cigarette packets, seeing other people smoke, etc.). According to this theory, if the schema is triggered, but smokers don’t get to take the drug for whatever reason, they get an urge. Once the schema is active, some mental resources will be allocated away from other functions in order to maintain the urge.

A study in 2003 investigated whether the urge is what causes poorer reaction times. (2) They also used the Sternberg task, and had three groups – a group allowed to smoke, a group deprived of cigarettes, and a group deprived of cigarettes but given nicotine patches. The people given patches had an equal urge to smoke a cigarette as the deprived group, but they got a nicotine fix. So it’s an ideal test of whether nicotine deprivation or the urge causes poor performance.

In the end, the deprived group had worse results than the patch group, who had worse results than the smoking group. Although the deprived group had the same urge to smoke as the patch group, they did worse on the test.

This shows that having the urge to smoke does interfere with the performance on this test; but it doesn’t tell the whole story. In addition to the effect of the urge, nicotine deprivation has some direct effect on the brain which slows down reaction times.

If you smoke, how often are you in a withdrawal state? Whenever you go without smoking for over an hour or so, you’re in withdrawal, and at least one of your mental functions – reaction time – is not as working as sharply as it could if you were a non-smoker. This has important ramifications – pop-ups! You’ll take longer to react click the ‘x’ of a pop-up window. You might even click the fake ‘x’, that just opens up another 10 pop-ups! I don’t know about you, but I think that’s as good a reason as any to quit.



(1) Tait, R., Martin-Iverson, M., Michie, P.T., Dusci, L. (2000). The effects of cigarette consumption on the Sternberg visual memory search paradigm. Addiction. 95(3), 437-446.
(2) Havermans, R.C., Debaere, S., Smulders, F.T.T., Wiers, R.W., Jansen, A.T.M. (2003). Effects of Cue Exposure, Urge to Smoke, and Nicotine Deprivation on Cognitive Performance in Smokers. Psychology of Addictive Behavious, 17(4), 336-339.


  • Christine says:

    Interestingly, there is also a link to mothers smoking while pregnant and ADHD. A 2009 study indicated that children whose mothers smoked during pregnancy have more than double the risk of being diagnosed with ADHD. It seems that nicotine (or something related to smoking ciagrettes) is linked to neurological function.

    That said, I think smoking has been demonized far beyond other ills. Not that I condone smoking while pregnant or smoking in general, I just think there are other lifestyle habits equally damaging to mind and body. Take a look at the people going through the drive-through window loading up on their double cheeseburger and fries. That is so bad for the body yet the fast-food junkies don’t get near the frowns as a smoker.

    • Warren Davies says:

      “That is so bad for the body yet the fast-food junkies don’t get near the frowns as a smoker.”

      Yeah, very true. Shall we begin the frowning ourselves? I haven’t had a MacDonalds for the longest time, but I remember getting one out of interest a while back. It tasted like fat and sugar, and I felt like crap afterwards. Best to keep that stuff to a minimum, I think…

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