Categories: 2012, October
Scott Kollins, PhD, MS
MORE THAN 440,000 DEATHS ARE ATTRIBUTED TO
CIGARETTE SMOKING ANNUALLY, making it the single most
preventable cause of death and illness in the United States. More than
one in five Americans above the age of eighteen smoke cigarettes, and in
spite of the well-known health risks associated with smoking, only a
small minority of regular smokers achieves prolonged abstinence.
These numbers take a turn for the worse in people who have ADHD, who are
at increased risk for cigarette smoking compared to those who do not
have the disorder. What do we know about the relationship between ADHD
and smoking? What are the evidence-based recommendations for clinical
management of smoking in the context of ADHD? What important areas are
in need of additional research? Here is what the science tells us.
association between ADHD and smoking
People with ADHD
smoke at rates significantly higher than the general
population. Data from a number of longitudinal studies
have shown clearly that individuals with ADHD are at increased risk for
cigarette smoking compared to their peers who do not have ADHD. For
example, one early longitudinal study examined individuals initially
identified as hyperactive (the term most consistent with a diagnosis of
ADHD when the study was initiated in 1974) and matched control
comparison children. By the age of seventeen, 46 percent of the
individuals initially diagnosed as hyperactive reported daily cigarette
smoking, compared to 24 percent of their age-mate controls. By
adulthood, 35 percent of the hyperactive group continued to report daily
cigarette smoking, compared to just 16 percent of the control
These data are consistent with a more recent study that examined 142
adolescents diagnosed with ADHD and 100 matched control comparison
adolescents who did not have ADHD. All the participants were between the
ages of thirteen to eighteen years. More than 30 percent of the group
with ADHD reported daily cigarette smoking compared to just over 12
percent of the individuals in the control group. Another study focused
on adults with ADHD reported that both males and females with ADHD
reported higher rates of cigarette smoking as compared to national data
for the general population. Importantly, ADHD is an independent risk
factor for smoking, even when other coexisting conditions like conduct
disorder and oppositional defiant disorder are controlled.
Individuals with ADHD start smoking at an
earlier age compared to the general population. The risk
for regular cigarette smoking among adolescents and adults with ADHD is
exacerbated by the fact that affected individuals typically start
smoking at earlier ages. For example, among thirteen- to
eighteen-year-olds with ADHD, the mean age of smoking the first
cigarette was 13.9 years, compared to 15.3 years for non-ADHD comparison
adolescents. Similarly, the mean age of regular smoking among the same
individuals was 16.3 years, compared to 17.4 years for the comparison
Another longitudinal study of children with and without ADHD similarly
reported that among those individuals reporting smoking in early
adulthood, 71 percent of the individuals with ADHD began smoking prior
to age 17, compared to 27 percent of the control participants who did
not have ADHD. So, not only are individuals with ADHD more likely to
become regular smokers at some point in their lives, but they start
earlier, thus resulting in greater overall exposure to smoking, which
significantly affects health outcomes.
Individuals with ADHD who try smoking
report greater likelihood of progression to regular smoking and higher
levels of nicotine dependence. Not everyone who
experiments with cigarette smoking progresses to regular smoking.
However, the presence of ADHD increases both the overall likelihood of
this progression and the speed with which it will occur. Smokers with
ADHD also report higher levels of nicotine dependence, an index of how
addicted these individuals are to smoking.
One study reported that more than twice as many individuals with a
childhood diagnosis of ADHD who were regular smokers reported lifetime
nicotine dependence compared to a comparison group. Similarly, in a
study of 80 people with ADHD and 86 comparison individuals who did not
have ADHD—all of whom reported smoking at some time in their
lives—scores on a standardized measure of nicotine dependence were
significantly higher among those with ADHD.
People with ADHD who smoke have a harder
time quitting. Although smoking cessation rates for the
general population are notoriously low, there is some evidence that
individuals with ADHD who smoke fare even worse when they try to quit.
Given the higher rates and greater severity of nicotine dependence
described above, this is not surprising.
One study examined quit ratios as an indicator of smoking cessation
success, defined as the percentage of individuals who reported ever
having smoked who defined themselves currently as ex-smokers. Nearly
twice as many individuals without ADHD who had a lifetime history of
smoking reported being an ex-smoker currently compared to the group with
ADHD . Very few studies have systematically examined smoking cessation
outcomes among those with ADHD. Some of these findings will be described
in more detail below.
Possible causes of
ADHD and cigarette smoking may
have common genetic origins. Molecular genetic
studies have identified similar candidate genes associated with both
ADHD and smoking, suggesting common neurobiological mechanisms may give
rise to this comorbidity.
One review identified seven genes that are consistently and
significantly associated with ADHD:
the dopamine D4 and D5 receptor genes
the dopamine transporter gene
the dopamine beta hydroxylase gene
the serotonin HTR1B gene
the serotonin transporter gene
the synaptosomal-association protein 25
Of these seven genes consistently shown to have association with ADHD,
six have also been shown to be associated with aspects of smoking
behavior. Variants of the DRD4, DAT, and DBH genes, as well as the HTR1B
and 5-HTT genes have been shown to be associated with higher levels of
smoking behavior in a range of populations. In addition, a haplotype of
the DRD5 gene has been shown to be protective against smoking
phenotypes. A range of other genes associated with smoking outcomes,
including the 5HTTLPR and variants of the MAO-A gene, have also been
shown to be associated with ADHD-related outcomes, though none have been
consistently replicated as a risk factor for the development of
Nicotine delivered via smoking may serve
as a form of "self-medication" for people with ADHD.
Nicotine exerts beneficial effects on a range of processes known to be
disrupted in individuals with ADHD, including attention, inhibitory
control, and working memory. As such, it has often been proposed that
those with ADHD are at heightened risk for smoking because of the
beneficial effects of nicotine across a range of cognitive
Support for this view comes from studies demonstrating that nicotine
administration enhances attention in smoking and non-smoking adults with
ADHD to a degree comparable to methylphenidate. Transdermal nicotine
alone and in combination with stimulant medication also reduces
self-reported ADHD symptoms.
In general, findings are mixed with respect to the so-called
"self-medication" hypothesis of the ADHD-smoking comorbidity. There has
been considerable inconsistency in the research definition with respect
to how the construct of self-medication is defined and measured. More
research is needed in this area to understand more about whether
nicotine and cigarette smoking serve to reduce the core ADHD symptoms
and therefore increase risk for regular smoking.
Very little work has been
conducted to understand how to reduce the risk for smoking among
individuals with ADHD or how to treat smoking or nicotine dependence in
those who already use cigarettes. One prospective study randomly
assigned non-smoking youth with ADHD to receive bupropion treatment or
placebo. They were subsequently followed for approximately five years.
The participants were also allowed to initiate stimulant treatment as
needed during the course of the trial. The results showed that bupropion
treatment did not influence the likelihood of cigarette smoking, but
that concurrent stimulant treatment was associated with lower risk of
initiating smoking and continuing smoking.
To date, only two published studies have been conducted to evaluate
smoking cessation interventions in smokers with ADHD. Both of these
studies examined nicotine replacement therapy alone and in combination
with approved stimulant medication for ADHD (OROS-methylphenidate and
lisdexamfetamine). Outcomes for both of these studies were
similar—smokers who received stimulant medication plus nicotine
replacement therapy fared no better than those who received nicotine
replacement therapy alone. In both studies, however, ADHD symptoms were
significantly improved in the groups who received the stimulant
medication, suggesting that the core symptoms of ADHD can be treated
effectively in the context of a smoking cessation attempt.
These findings are important, since several small laboratory studies
have been published showing that administration of stimulant drugs
increases cigarette smoking in both ADHD and non-ADHD smoking. Also
of note, in the larger of the two clinical trials, there was evidence
that OROS-methylphenidate did significantly facilitate smoking cessation
compared to placebo among non-Caucasian smokers with ADHD.
for future research
Given the well-documented association between ADHD and
cigarette smoking, the most important areas of future research must help
us better understand this link in order to develop more effective
prevention and treatment programs. In addition to the genetic and
pharmacological factors discussed above, other important psychosocial
factors, such as familial smoking, peer relations, and academic
functioning, have all been shown to contribute to smoking risk in
children with ADHD. Future research should capitalize on what we know
about these areas to begin to develop creative and targeted prevention
programs for youth with ADHD. Basic science, such as molecular genetic
and neuroimaging research, can also contribute to the development of
Reducing the risk
In the absence of controlled studies, there are no
specific interventions that can be recommended to reduce the risk of
smoking in kids with ADHD. Some general recommendations may still help
reduce risk, however.
Kids are more likely to smoke if their family members or friends do. If
you smoke and do not want your child to smoke, quit now. Similarly,
parents should be aware of their child or adolescent’s peer group
For clinicians treating patients with ADHD who are already smokers, it
seems that use of stimulant medication does not have a negative impact
on cessation for those interested in quitting. More research needs to be
done, however, on the effects of stimulant medication in smokers with
ADHD who are not interested in quitting.
Nicotine replacement therapy seems to work equally as well for smokers
with ADHD as it does for the general population. Overall, clinicians
treating smokers with ADHD should monitor smoking levels—if
possible via objective or biochemical means—to ensure that
treatment for ADHD is not adversely affecting smoking behavior.
FOR MORE INFO
CHADD’s board of directors has made smoking a top
priority. We want every member to know several key facts:
Tweens and teens with ADHD are more likely to smoke
and smoke at an earlier age.
Smokers with ADHD have a far more
difficult time quitting than smokers without ADHD.
Pregnant mothers who smoke are far more
likely to have children with ADHD.
The percentage of people with ADHD who
are smokers are twice as likely to be smokers than people without
To address this major health hazard for our members, CHADD is
planning several initiatives:
Advocate for better research
funding to address, prevent, and treat smoking in the population
affected by ADHD.
Seek funding for a consensus conference
on smoking and ADHD.
Seek funding for a campaign to prevent
smoking among tweens and teens with ADHD.
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