ReviewPrevalence of attention-deficit hyperactivity disorder in substance use disorder patients: A meta-analysis and meta-regression analysis
Introduction
Substance use disorders (SUD) are a major public health problem. The Epidemiologic Catchment Area Study reports a lifetime prevalence for alcohol use disorders of 13.5% and for other drug use disorders of 6.1% (Regier et al., 1990), and in the Netherlands Mental Health Survey and Incidence Study-2 a lifetime prevalence of 19.1% for any substance use disorder was found (de Graaf et al., 2011). Patients with SUD constitute a large proportion of mental health service users, and are overrepresented in general medical care (Cherpitel and Ye, 2008).
Attention Deficit Hyperactivity Disorder (ADHD) is a major risk factor for the development of substance use disorders (Biederman et al., 1995, Lee et al., 2011, Charach et al., 2011), either directly (Szobot et al., 2007) or mediated by conduct disorder (Fergusson et al., 2007). Comorbid ADHD has a negative effect on the course of SUD. Patients with both ADHD and SUD become addicted at a younger age, use more substances and are hospitalized more often than SUD patients without ADHD (Arias et al., 2008). ADHD is also associated with higher relapse rates after successful addiction treatment (Carroll and Rounsaville, 1993). Moreover, treatment studies have consistently shown that pharmacological treatment of ADHD with methylphenidate or atomoxetine is not as effective in ADHD patients with SUD compared to those without this comorbidity (Carpentier et al., 2005, Levin et al., 2006, Levin et al., 2007, Konstenius et al., 2010, Castells et al., 2011, Wilens et al., 2008a, Wilens et al., 2008b, Thurstone et al., 2010). Only one study reported a decrease in self-reported ADHD symptoms after treatment in SUD patients (Schubiner et al., 2002). Other treatment strategies such as cognitive behavioural therapy (Safren et al., 2010) have not been studied in this population.
In order to develop optimal treatment programs for patients with ADHD and SUD, it is important to adequately recognize and diagnose these disorders. This may be complicated by overlapping symptoms, such as effects of drug intoxication or withdrawal (Levin, 2007). While the prevalence of ADHD among children in the general population is approximately 5% (Polanczyk and Rohde, 2007), and in adults around 4% (Kessler et al., 2006), it is often assumed that the ADHD prevalence in SUD patients is higher. However, prevalence estimates in the literature vary considerably and range from 2% in a study by Hannesdottir and colleagues (Hannesdottir et al., 2001) to 83% in a study by Matsumoto and colleagues (Matsumoto et al., 2005). It is currently unclear whether differences in substance of abuse, in ADHD or SUD assessment, or between SUD populations may explain this variation in prevalence estimates. The current study aims to establish a best estimate of the prevalence of comorbid ADHD in adolescents and adults with SUD, using data from high quality studies in a statistical meta- and meta-regression analysis. Differences between studies in terms of patient population, primary substance of abuse, setting and assessment procedure are taken into account. A meta-analytic review of the existing studies to date is important to obtain a more accurate estimate of the comorbidity of ADHD and SUD, as a first step in developing adequate diagnostic and treatment programs for this patient population.
Section snippets
Data sources
We conducted a systematic literature search to identify studies reporting on the prevalence of comorbid ADHD in SUD populations using MEDLINE, PsycINFO and EMBASE. Key words for the search were: ADHD, substance-related disorders (Mesh term MEDLINE), addiction (subject heading in EMBASE), drug abuse, drug dependence, alcohol abuse, alcoholism (key words PsycINFO), comorbidity, and prevalence. English language and human studies were used as limits. Databases were searched from 1966 until January
Results of literature search
Fig. 1 shows the process of identifying and selecting relevant articles. Searches in MEDLINE, PsycINFO and EMBASE yielded a total of 1040 non-duplicate articles. After screening of titles and abstracts, 59 articles were fully studied by two authors on eligibility, and an additional nine studies were added for eligibility assessment from cross-references. A total of 39 of the 68 studies were excluded for various reasons, which resulted in a final inclusion of 29 articles. A more detailed list of
Discussion
In this statistical meta-analysis, we provide a best estimate of ADHD prevalence in SUD populations, based upon all currently available studies of sufficient quality and adjusted for a range of variables potentially affecting prevalence. Results indicate that the overall prevalence is approximately 23%, irrespective of age and gender, ethnicity, duration of abstinence, time-frame, and setting. A series of meta-regression analyses showed that the prevalence of ADHD is significantly lower in
Role of funding source
No financial support was received for this study.
Contributors
KE, GG and RS managed literature searches. Analyses were performed by KE, MS and FS. KE, WB and RS led the drafting of the manuscript. GG, CC, FS and MS revised the manuscript. All authors contributed to and approved of the final version of this manuscript.
Conflict of interest
The authors report no financial or other relationship relevant to the subject of this article.
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