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Pr Nora Volkow: Why ADHD patients are heavy smokers?

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Attention Deficit Hyperactivity Disorder increases the risk of tobacco smoking.





Hello! You’re on MD-FM INSIGHT, the first medical web radio. Today we’ll be devoting our "Question & Answer" program to understanding why patients with attention deficit hyperactivity disorder (or ADHD) are such heavy tobacco smokers. At the last meeting of the American Psychiatric Association, in San Francisco, we interviewed Pr. Nora Volkow, director of the United States National Institute on Drug Abuse, on this subject:




Pr. Volkow, first of all, can you tell us why we think people with ADHD are much more susceptible to cigarette smoking than others?



“What we think is going on is that the brain of ADHD individuals is much less sensitive to rewards. And, as a result of that, they are not motived by stimuli that allow you to perform, for example, well at school. And thus smoking makes them temporarily much more sensitive to rewards. And that may be one of the factors that underlie the high risk of smoking as well as the difficulties that they have quitting smoking.  So: some people may be smoking to auto-medicate themselves. They smoke to be able to sustain attention, to improve their cognitive performance, to perceive other things more rewarding, and to feel better –to have a better sense of mood.



Ok and: why are these patients much less sensitive to reward… Do we have an idea of what’s going on?



“Overall the studies have consistently shown that there is a decrease in activity of dopaminergic pathways... Also stimulant medications, which are the most effective medications that we have for ADHD, enhance dopaminergic signaling. So it is very consistent that there is an impaired activity of the dopaminergic pathways.”



But wasn’t there some kind of controversy about the role of dopamine signaling in ADHD?



“There has been controversy vis-à-vis a marker that brain-imaging researchers have been using to document abnormalities in dopamine function —that’s where the whole controversy has been. And that marker is the dopamine transporter, which is what is affected by stimulant medication. So some studies have shown increases, others have shown decreases and others have shown no changes. So that’s where there is a controversy –but not in dopamine signaling.”



Ok and so what’s the relationship between dopamine signaling and cigarette smoking?



“You have nicotine receptors directly on the dopamine cells. So when someone smokes nicotine and those nicotine receptors are activated, what you do is increase the firing of dopamine cells, which in turn leads to activation of reward systems but also other systems modulated by dopamine that are implicated in attention. So when a person that has ADHD smokes, what you see (and it’s same thing if you give them nicotine and nicotine patch) is that they can sustain attention for much longer periods of time and that there’s improvement in their responses to reward.”



And is nicotine the only substance in cigarettes to have an effect?



“Chemicals other than nicotine may be involved in the reasons why people may be smoking. So it comes back to the notion that not everybody smokes cigarettes just to feel high, they smoke to feel better.  And for example, we know that chemicals in the smoke of cigarette inhibit monoamine oxidase and drugs that inhibit monoamine oxidase A have antidepressant properties. So it may be for example that patients who are depressed, who are at greater risk of smoking may be smoking not just for the nicotine  but by inhibiting monoamine oxidase A, they might be getting antidepressant benefits.”



And I think patients with schizophrenia also tend to be heavy smokers. Is it the same phenomenon going on there?  



“These are two diseases that are distinct, and in schizophrenia for example we know that they may be smoking because it improves the ability of their brain to process sensations from the outside –So they can process them better. That is not the problem in ADHD, in ADHD it’s more a problem of a decreased sensitivity to reward, and therefore you cannot sustain motivation and there is an impairment on attentional processes. And nicotine improves both: it improves the sensitivity to reward, and nicotine improves attentional processes. But both of them, to answer your question, may be auto-medicating but for different effects of nicotine.”



So what’s your take home message?



“So: some people may be smoking to auto-medicate themselves, and it is very likely that this starts actually very early on in adolescence. And therefore the importance, when you have an adolescent who is smoking very early on, or just smoking, you need to make a differential, that there’s not an underlying mental illness and that should include ADHD.  Because the same question pertains: could it be that someone that has a mood disorder may be medicating themselves by nicotine because they will feel better… So it’s important to make a differential diagnosis. And when you have someone that is already diagnosed, and they are on medication, and they are still smoking, you then need to ask the question: is the medication being sufficiently effective to manage the symptoms of ADHD. Or could the patient be trying to manage them better by smoking.”




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