Attention-Deficit/Hyperactivity Disorder and Substance Use: Symptom Pattern and Drug Choice

Abstract

While there has been much recent interest in the relationship between attention-deficit/hyperactivity disorder (ADHD) and substance use disorders (SUDs), little has been reported about ADHD diagnostic subtypes, persistence of symptoms from childhood into adulthood, and substance of choice in individuals with substance use disorders (SUD+) and comorbid ADHD. To examine the prevalence and subtypes of ADHD in a group of SUD+ individuals, 136 inpatients with an SUD diagnosis (cocaine vs. alcohol vs. cocaine/alcohol) were administered a structured interview for ADHD. Of the SUD+ individuals, 32% met criteria for ADHD, and 35% of those with a childhood diagnosis of ADHD continued to have clinically significant symptoms into adulthood. There were no significant differences in the percentage of ADHD between the SUD+ groups divided by drug choice. Of ADHD subtypes, subjects with combined and inattentive types were significantly more likely to have symptoms continue into adulthood (p ≤. 05) than the hyperactive/impulsive subtype. Patients with cocaine use were more likely to have ADHD in childhood only when compared to the alcohol or cocaine-alcohol groups. The findings of this study indicate that ADHD is prevalent in treatment-seeking substance users without difference in prevalence or subtype by drug choice.

Full text

AM. J. DRUG ALCOHOL ABUSE, 25(3), pp. 441–448 (1999)
Attention-Deficit/Hyperactivity
Disorder and Substance Use:
Symptom Pattern and Drug Choice
Chrissie Clure, M.D.
Kathleen T. Brady, M.D., Ph.D.*
Michael E. Saladin, Ph.D.
Diane Johnson, Ph.D.
Randy Waid, Ph.D.
Margaret Rittenbury, M.D.
Medical University of South Carolina
Department of Psychiatry
Charleston, South Carolina
ABSTRACT
While there has been much recent interest in the relationship between attention-deficit/hyper-
activity disorder (ADHD) and substance use disorders (SUDs), little has been reported about
ADHD diagnostic subtypes, persistence of symptoms from childhood into adulthood, and
substance of choice in individuals with substance use disorders (SUD⫹) and comorbid
ADHD. To examine the prevalence and subtypes of ADHD in a group of SUD⫹individuals,
136 inpatients with an SUD diagnosis (cocaine vs. alcohol vs. cocaine/alcohol) were adminis-
tered a structured interview for ADHD. Of the SUD⫹individuals, 32% met criteria for
ADHD, and 35% of those with a childhood diagnosis of ADHD continued to have clinically
significant symptoms into adulthood. There were no significant differences in the percentage
of ADHD between the SUD⫹groups divided by drug choice. Of ADHD subtypes, subjects
with combined and inattentive types were significantly more likely to have symptoms continue
into adulthood (pⱕ.05) than the hyperactive/impulsive subtype. Patients with cocaine use
were more likely to have ADHD in childhood only when compared to thealcohol or cocaine-
alcohol groups. The findings of this study indicate that ADHD is prevalent in treatment-
seeking substance users without difference in prevalence or subtype by drug choice.
* To whom correspondence should be addressed at Professor of Psychiatry, Medical University
of South Carolina, Department of Psychiatry, CDAP, 850 MUSC Complex, Suite 553, Charleston,
SC 29425. Telephone: (803) 792-5215. Fax: (803) 792-7353.
441
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442 CLURE ET AL.
INTRODUCTION
Attention-deficit/hyperactivity disorder (ADHD) has received much attention
recently in the lay press, as well as in the scientific community. At one time, this
disorder was thought to affect approximately 6–9% of school-aged children and
usually to disappear during adolescence and adulthood. However, over the last
several years, investigation has focused on the persistence of this disorder into
adulthood. Follow-up studies have shown that as many as 30–50% of children
with ADHD continue to have clinically significant symptoms into adulthood
(1–3).
While some recent investigation regarding adult ADHD has demonstrated the
persistence of this disorder beyond adolescence and the high prevalence of many
associated comorbidities, there has been little attention focused on how the condi-
tion is expressed in adulthood. There is limited information regarding the degree
and type of symptomatology, the actual symptoms that persist, or whether the
symptoms present in childhood modify or change in adulthood. Mannuzza et al.
(1) reported, in a prospective follow-up study of males diagnosed with childhood
ADHD, that the disorder fairly consistently persisted into adolescence. By adult-
hood, however, the number of subjects that met the full diagnosis of ADHD had
decreased substantially. Hill and Schoener (4), in a review of nine prospective
studies, reported that nearly all cases of childhood ADHD diminish over the
course of time. It has been suggested that some of this dramatic decline in symp-
toms between adolescence and adulthood is due to a change in symptom charac-
teristics with maturity rather than remission of the disorder (2). Murphy and Bark-
ley (5) suggest that the current diagnostic thresholds for the adult disorder are
too stringent and likely lead to underdiagnosis.
An important recent concern related to ADHD is the high prevalence of com-
orbidity with substance use disorders (SUDs). Many investigators have noted
that ADHD occurs in substance users at a rate significantly higher than that in
the general population. Carroll and Rounsaville (6) reported a 35% prevalence
of ADHD in treatment-seeking cocaine abusers. Tarter, Kirisci, and Mezzich (7)
also reported elevated rates of ADHD in alcohol-dependent patients compared
to the rate in the general population. In spite of the evidence supporting an associ-
ation between adult ADHD and substance abuse, little attention has been focused
on the nature of this relationship, especially with regard to the substance of choice
and the subtype of ADHD in individuals with comorbid ADHD and SUDs. It is
also possible that the development of an SUD may influence the persistence of
childhood ADHD symptoms into adulthood and/or influence the presentation of
ADHD in adulthood. There have been no investigations specifically examining
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ATTENTION-DEFICIT/HYPERACTIVITY DISORDER 443
subtypes of ADHD in childhood and adulthood and persistence of specific symp-
toms in a population with substance use disorder (SUD⫹).
The present study was designed to examine the prevalence and subtypes of
ADHD in a group of SUD⫹adults divided by drug choice. It was hypothesized
that more ADHD would be found in a cocaine-dependent population compared to
other substance-dependent groups. Symptom persistence and changes in ADHD
subtype from adolescence to adulthood was also examined.
METHODS
From three inpatient substance abuse treatment facilities, 136 subjects were
recruited and divided by primary substance choice into one of the following cate-
gories: cocaine dependence, alcohol dependence, and cocaine and alcohol depen-
dence. At least 3–5 days after last drug or alcohol use, subjects were administered
the CHAMPS interview (8) for ADHD. Psychiatric and substance use diagnoses
were made by semistructured interview using DSM-IV criteria. The CHAMPS
consists of 26 questions, with Parts A and B addressing childhood and adulthood
symptoms, respectively. This instrument is divided into three sections, with each
section addressing one of the following symptom clusters: inattention, impulsiv-
ity, and hyperactivity. To receive a diagnosis of adult ADHD, individuals had
to meet full diagnostic criteria before the age of 7 and continue to meet criteria
at the time of assessment. Diagnosis was based on self-report only. Individuals
who met criteria for adult ADHD fell into one of the four DSM-IV ADHD diag-
noses: combined type (full diagnosis), inattentive type, hyperactive impulsive
type, and ADHD NOS (not otherwise specified; four DSM-IV criteria).
STATISTICAL ANALYSES
Independent sample ttests were employed in comparisons involving continu-
ous variables, and chi-square tests of association were employed with categorical
variables. Because there were a considerable number of statistical comparisons
made in this study and since multiple comparisons result in an inflation of the
Type I error rate (i.e., inflated α), a modified Bonferroni correction procedure
was implemented (9). The αlevel associated with the application of the modified
Bonferroni correction procedure—Bonf. α⫽[(desired per comparison α/num-
ber of comparisons)* 2)]—and the per-comparison αlevel are specified at the
bottom of each figure.
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444 CLURE ET AL.
Table 1. Demographics of ADHD⫹Versus ADHD⫺of SUD⫹Group
ADHD⫹ADHD⫺
(n⫽43) (n⫽93) Statistic
Sex (% male) 81% 73.1% n.s.
Age 34.3 (⫾1.0) 34.3 (⫾.69) n.s.
Race 50% white 32.3% white n.s.
50% African-American 66.7% African-American n.s.
Employment (% employed) 67% 70% n.s.
Marital status (% married) 53% 58% n.s.
RESULTS
Demographics
In Table 1, the demographic characteristics of the group are displayed. Of the
136 treatment-seeking SUD⫹subjects, 43 (32%) screened met criteria for one
of the four subtypes of ADHD, and 15% (n⫽21) had current ADHD. There
were no significant differences between individuals with or without ADHD on
any demographic variables.
Figure 1 depicts the number of ADHD⫹individuals divided by substance of
choice. In this figure, the population is also divided into those who met ADHD
criteria in childhood only and those who continued to meet criteria as adults.
Approximately 49% (21/43) of SUD⫹subjects who met ADHD criteria in child-
hood continued to have clinically significant symptoms into adulthood. As can
Fig. 1. ADHD by substance choice in SUD⫹subjects, childhood only versus current diagnoses.
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ATTENTION-DEFICIT/HYPERACTIVITY DISORDER 445
Fig. 2. ADHD subtypes in SUD⫹subjects, childhood only versus current diagnoses.
be seen, there were no significant differences in the number of ADHD⫹subjects
found in the groups divided by substance of choice. In the cocaine group, 63%
of subjects with an ADHD diagnosis had their symptoms resolve by adulthood;
45% of ADHD⫹subjects in the alcohol group had their symptoms resolve by
adulthood.
Figure 2 displays the ADHD subtypes in the population studied. Again, the
population is divided into those who met criteria in childhood only and those
who continue to meet criteria as adults. As can be seen, 77% (10/13) of the
individuals with the combined ADHD diagnosis and 75% (6/8) of those with the
inattentive type continued to meet criteria for ADHD as adults, while only 8%
(1/13) of those in the hyperactive subgroup continued to meet criteria as adults.
Individuals with the hyperactive/impulsive subtype and ADHD NOS were more
significantly likely than the inattentive or combined subtypes to meet diagnostic
criteria in childhood only.
In Table 2, the percentages of individuals with ADHD subtypes divided by
lifetime ADHD, childhood only ADHD, and current ADHD are displayed. As
can be seen, the hyperactive subtype of ADHD is the most common subtype in
Table 2. Percentage of ADHD Subtypes in SUD⫹Subjects
Lifetime (%) Childhood only (%) Current (%)
Combined 30 14 44
Inattentive 18 10 26
Hyperactive 30 57 4
NOS 22 19 26
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446 CLURE ET AL.
individuals with ADHD in childhood only, and it is the least common subtype
in individuals currently with ADHD.
DISCUSSION
There were some interesting positive and negative findings in this study. The
finding of 15% prevalence of current ADHD and 32% lifetime ADHD in this
treatment-seeking substance use population is lower than that reported by some
investigators, but is consistent with other reports (10). Our requirement for the
diagnosis of childhood ADHD before age 7 may have decreased our prevalence
estimates relative to those found in other studies, in which less stringent criteria
have been applied. This is much higher than in the general population, in which
it is approximated that 6–9% (11, 12) of school-aged children have ADHD. This
is consistent with previous studies that show a high incidence of ADHD in SUD⫹
populations (6, 7, 9). The lack of difference in employment or marital status in
the SUD⫹group between individuals with or without ADHD is interesting. It
would be expected that the ADHD⫹group would function at a lower level and
be less employable, yet this does not appear to be the case. It is likely that the
presence of substance dependence was a stronger factor in determining level of
function in the SUD⫹group.
The finding that there were no differences in the presence of ADHD or in
ADHD subtypes when divided by substance of choice did not support the original
hypotheses. Because stimulants are an effective treatment for ADHD, it seems
plausible that individuals with ADHD may be likely to choosestimulants to self-
medicate symptoms of ADHD (13). There have been reports of stimulant abuse
as self-medication for ADHD (14). In this study, however, both alcohol and
polysubstance use were just as likely to co-occur with ADHD. Other investigators
have commented on ADHD as a risk factor for substance abuse in general (1) .
It may be that some of the characteristics often seen in individuals with ADHD,
such as impulsivity and poor school performance, predispose use of any sub-
stance, not stimulants in particular.
There were some interesting findings with regard to persistence of ADHD
symptoms and subtypes from childhood into adulthood. Approximately 15% of
the SUD⫹group (n⫽22) met criteria for ADHD in childhood only. The preva-
lence of ADHD was high, and the percentage of subjects with the persistence of
ADHD symptoms from childhood into adulthood (21/43, 49%) is on the high
end of that reported in the general population (30–50%). Of interest is the fact
that, when divided by substance of choice, individuals with cocaine dependence
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ATTENTION-DEFICIT/HYPERACTIVITY DISORDER 447
were most likely to meet criteria for childhood ADHD only. It is possible that
current symptoms of ADHD are being masked by cocaine use. When considering
the similar pharmacologic properties of cocaine and stimulant medications used
successfully in the treatment of ADHD, this explanation has some intuitive ap-
peal. Clearly, monitoring ADHD symptoms during lengthier times in abstinence
in the cocaine-dependent group would be necessary to explore this hypothesis.
Other substantial differences between ADHD subtypes with regard to the con-
tinuation of clinically significant symptoms of ADHD into adulthood in the
SUD⫹group were observed. Individuals with the combined and inattentive sub-
types of ADHD were significantly more likely than those with the hyperactive/
impulsive subtype of ADHD to meet criteria for ADHD as adults. Others have
reported that the inattentive subtype of ADHD is more likely than the hyper-
active/impulsive subtype to persist into adulthood in non-substance-dependent
individuals (15).
In conclusion, while limited by small sample size, there are several interesting
findings. Consistent with other investigations, we found a high prevalence of
ADHD in this substance abuse treatment-seeking population. However, there did
not appear to be any substantial differences in ADHD prevalence by substance
of choice. Specifically, there was no higher prevalence of ADHD in the cocaine
group, as might be predicted by the self-medication hypothesis. The combined
and inattentive subtypes of ADHD were most likely to be persistent into adult-
hood. Cocaine-dependent individuals were somewhat less likely to exhibit persis-
tent ADHD symptoms in adulthood compared to the alcohol-dependent group.
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