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Categories: 2012, October
by David Teplin, PsyD
ADULT ADHD RARELY OCCURS BY ITSELF. Often, it coexists
with other clinical disorders, including anxiety disorders, mood
disorders, tic disorders, sleep disorders, substance use disorders, and
personality disorders. The co-occurrence of ADHD and substance use
disorders has been the subject of recent studies. Like ADHD, substance
use disorders have profound social, psychological, and economic
The high heritability of ADHD and SUDs seen in both twin and adoption
studies suggests that there is considerable overlap in the genetic
influences between them. The high rate of co-occurrence between such
disorders also suggests some shared underlying neurobiological
mechanisms may be at play.
Shared neurobiological mechanisms
Brain-imaging studies suggest similarities between people with ADHD
and people with addiction-related craving. A possible explanation is
that those with addiction have stronger cravings when they also suffer
from ADHD, and that adequate treatment of ADHD actually reduces the
craving and helps prevent relapses into substance use.
In addition to cravings, impulsivity is a risk factor for substance use,
and poor inhibitory control is also a feature of ADHD. As such, the
thinking has been that there is a common brain network that underlies
such impulsivity in both disorders. Recent brain-imaging research,
however, suggests that the brain networks underlying both disorders are
actually distinct, and that impulsive behavior may result from one of
several different brain networks.
While ADHD and SUDs are distinct, independent disorders, people affected
by either or both often have a deficit of the neurotransmitter dopamine
in the brain. Also, all addictive drugs strongly stimulate dopamine
through which they excite the reward system, as well as learning,
memory, and behavior.
Underfunctioning of dopamine is associated with reduced perception of
reward, worsening cognition, and difficulty inhibiting behavior. This
makes life boring, worsens the ability to recognize future negative
consequences, and reduces the ability to ignore an inviting distraction.
This is commonly found in both disorders. Additionally, the cognitive
dysfunction associated with ADHD may decrease a person's ability to
assess the negative consequences of substance abuse and to delay
immediate gratification from drug or alcohol use.
Compared to individuals without the disorder, people with ADHD are at
more than a six times greater risk of developing an SUD. Individuals
with ADHD experience an earlier age of onset and a longer duration of
SUDs. Those with both ADHD and SUD may take longer to achieve remission
and are likely to have longer courses of treatment and poorer outcomes.
Thus, ADHD is a risk factor for SUDs.
Substance use disorders are highly prevalent in adults with ADHD, and
conversely, ADHD is overrepresented among those persons with SUDs. Up to
forty-five percent of adults with ADHD have a history of alcohol abuse
or dependence, and about one-third have a history of illegal drug abuse
or dependence. Marijuana, nicotine, alcohol, and cocaine appear to be
the most commonly used substances among this population.
It is estimated that thirty-five to seventy-one percent of alcohol
abusers and roughly fifteen to twenty-five percent of
substance-dependent patients also have ADHD. Adults with ADHD and
co-occurring SUD report earlier onset and greater severity of their SUD
than adults without ADHD.
People with ADHD also experience earlier onset of tobacco smoking and
show higher rates by mid-adolescence. Knowing that ADHD actually
increases the risk of nicotine addiction highlights the importance of
prevention efforts aimed at the adolescent population and their
families. There may also be biological mechanisms underlying both ADHD
and nicotine dependence. Nicotine-based medications can treat ADHD
symptoms, and it is now known that children of mothers who smoked during
pregnancy are at a much greater risk of having ADHD.
While those with ADHD are more likely to begin smoking than those
without, smoking cessation is less likely among those individuals.
Evidence suggests that nicotine improves attentiveness and performance
deficits amongst those with ADHD, which provides a self-medicating
rationale that nicotine increases dopamine release in the brain.
People with ADHD are more vulnerable to SUDs if they also have a
co-occurring condition, such as oppositional defiant disorder, bipolar
disorder, or conduct disorder. Individuals with ADHD and conduct
disorder are estimated to be almost nine times more likely to develop an
SUD before age eighteen, compared with those with ADHD alone. Impaired
executive functioning, behavioral dyscontrol, impulsivity, and peer
rejection are common in both ADHD and conduct disorder and therefore may
increase the risk of developing SUDs in individuals with both
For the clinician, detecting SUDs in patients with ADHD can be
challenging. Ideally, the best time to assess for ADHD symptoms is after
prolonged abstinence from any influencing substance. However, in most
clinical situations this is not practical. Perhaps a better approach is
the longitudinal assessment for ADHD symptoms. Detailing evidence of
early childhood onset of ADHD symptoms before the patient began using
substances, and/or that persisted through periods of prolonged
abstinence from substances, can be helpful in conducting a proper
When assessing for SUD risk, it is also important to consider the
person's clinical condition, history of comorbid conditions that suggest
SUDs, overall functional status, as well as collateral information from
family members about the person's behavior and substance abuse.
Factors that can influence a person’s risk of developing SUDs
include their clinical condition, a history of co-existing conditions
that suggest SUDs, and overall functional status. Along with collateral
information from family members about the person’s behaviors and
history of substance abuse, these factors can help assess the
person’s risk of developing an SUD.
Treatment for people with coexisting ADHD and active SUDs should occur
together. However, if possible, the SUDs should be initially treated to
try and ensure stabilization. Since people with ADHD and active SUD are
more likely to have severe SUD and a worse prognosis, many may relapse
prior to obtaining ADHD treatment. Therefore, combined treatment
approaches may be best, including cognitive-behavioral therapy,
contingency management, motivational interviewing, family therapy, and
mutual support groups.
Treatment with medication
Some clinicians prefer to stabilize the SUD before initiating
stimulant medication when treating co-occurring ADHD and SUD. Others
prefer to use nonstimulants as a first-line treatment rather than
stimulants, due to issues such as potential abuse, diversion, and a
history of stimulant or amphetamine use problems. Nonstimulants have not
demonstrated the same efficacy as compared to stimulants for treating
To minimize the risk of SUDs when treating such patients with
stimulants, longer-acting stimulant formulations are preferred over
short-acting ones because they are less likely to be abused. Both close
supervision and monitoring are recommended, including toxicology
While stimulant medication may improve retention in addiction treatment,
and in some cases, may decrease harm from substance use, stimulants have
not been particularly effective in decreasing drug use, per se. As the
prevalence of comorbidity is high in ADHD, there is a relatively high
rate of treatment drop-out, as well as noncompliance with taking
Some researchers have expressed concern that exposure to stimulant
medication early on in childhood could predispose patients to future
substance abuse. There is also the suggestion that early exposure to
stimulants could increase the risk of later SUDs by "priming" the brain,
which then becomes more receptive to illicit drug exposure.
Although there have been concerns that the use of stimulant medication
does increase SUD risk, recent evidence suggests that stimulant
medication use does not increase susceptibility to SUDs. Other studies
suggest that the use of stimulant medication in ADHD patients may
actually protect against SUDs.
Those children with ADHD who were treated with stimulant medication
until adolescence were between three to six times less likely to develop
SUDs compared to those who did not receive stimulant medication. This
protective effect decreased when patients were followed into adulthood,
but those treated with stimulant medication were still almost one and a
half times less likely to develop SUDs than those who were not treated
with stimulant medication. One possibility is that the use of stimulant
medication may delay, but not prevent SUDs. Another possibility is that
by adulthood, loss of parental supervision may lead to poor medication
compliance, and therefore, increased susceptibility to SUDs.
As ADHD is a risk factor for SUDs, and because there is great overlap
between these two distinct disorders, it is imperative that anyone being
evaluated for adult ADHD also be assessed for the possible presence or
history of SUDs. Failure to do so not only affects the diagnosis, but
can have an enormous impact on the effectiveness and outcome of
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