Efficacy of methylphenidate, psychosocial treatments and their combination in school-aged children with ADHD: A meta-analysis

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Abstract

Introduction

This meta-analysis compares effect-sizes of methylphenidate and psychosocial treatments and their combination on ADHD, concurrent oppositional, conduct symptoms, social behaviors and academic functioning.

Method

Several databases (PubMed, PsycInfo, ISI Web of Science) were searched for articles published between 1985 and September 2006. Inclusion criteria were: a diagnosis of ADHD; age from 6–12 years; a randomized controlled treatment design; efficacy established with parent and teacher rating scales; psychosocial treatments used were described as behavioral or cognitive-behavioral; the methylphenidate treatment was short-acting; and finally, treatment was conducted in a clinical setting.

Results

ADHD outcomes showed large mean weighted effect-sizes for both methylphenidate and combined treatments, psychosocial treatments had a moderate mean weighted effect-size; a similar pattern emerged for oppositional and conducted behavior symptoms. Social behavior outcomes showed comparable moderate mean weighted effect-sizes for all treatments, while on academic functioning, all treatments had low mean weighted effect-sizes. There was no correlation between duration of psychosocial treatment and effect-size.

Conclusions

Both methylphenidate and psychosocial treatments are effective in reducing ADHD symptoms. However, psychosocial treatment yields smaller effects than both other treatment conditions. Psychosocial treatment has no additional value to methylphenidate for the reduction of ADHD and teacher rated ODD symptoms. However, for social behavior and parent rated ODD the three treatments were equally effective. For improvement of academic functioning no treatment was effective.

Introduction

Attention-Deficit Hyperactivity Disorder [ADHD] is one of the most common disorders among school-aged children, with a prevalence of 3–7% in the general population (Diagnostic and Statistical Manual of Mental Disorders, fourth edition revised [DSM-IV-R], American Psychiatric Association [APA], 2000). The most frequent comorbid conditions are oppositional defiant and conduct disorder (August, Realmuto, MacDonald, Nugent & Crosby, 1996). Further, children with ADHD often show academic deficiencies (Jensen, Martin, & Cantwell, 1997) and deficient social skills (Van der Oord et al., 2005).

It has generally been agreed in the empirical literature that only two treatments and their combination have been validated as effective short-term treatment modalities for school-aged children with ADHD: psychosocial treatments (behavioral or cognitive-behavioral treatments), stimulant treatments (mostly methylphenidate), and the combination of both (Richters et al., 1995, Kutcher et al., 2004). The benefits of short-term treatments with stimulants have been relatively well documented (e.g., Schachter et al., 2001, Spencer et al., 1996, Swanson, 1993), but the empirical evidence for long-term efficacy of stimulants has been meager (Schachar et al., 2002, Schachter et al., 2001). The efficacy of psychosocial treatments alone and the combination of stimulant treatment and psychosocial treatments is less well documented (Pelham, Wheeler, & Chronis, 1998). In fact, the number of studies that have involved stimulant treatments far exceeds the number of studies that have evaluated the effects of psychosocial interventions (Pelham et al., 1998).

Studies of the short-term beneficial effects of stimulants on the symptoms of ADHD constitute the largest body of treatment literature on any childhood-onset psychiatric disorder (Greenhill, Halperin, & Abikoff, 1999). About 70% of the children with ADHD respond when a single stimulant is tried. If another stimulant is tried after stopping a failed trial with an initial medication, a clinical response of up to 90% can be achieved (Spencer et al., 1996).

Children treated with stimulants, however, often show side effects (Schachter et al., 2001). For example, about 1 in 4 children treated with stimulants report decreased appetite, and about 1 in 7 children report insomnia (Schachter et al., 2001). A further disadvantage of methylphenidate is that it does not cover very important home routines, such as the morning or bedtime routines. Sustained release methylphenidate, however, covers most of the day. Short-term studies have reported that improvement due to stimulants is most salient on ADHD symptoms; on long-term academic achievement and social skills, stimulants have failed to show consistent benefits (Greenhill et al., 1999, Whalen and Henker, 1991). Improvement, however, is not maintained when medication is discontinued (Abikoff et al., 2004a, Abikoff et al., 2004b). Further, lack of improvement in peer relationships is a disadvantage of medication treatment (Hoza et al., 2005). A review of several meta-analyses on methylphenidate also shows that the most robust effect of methylphenidate is shown on core symptoms as hyperactivity, inattention and impulsivity, and that on academic achievement the results of methylphenidate have been less pronounced (Conners, 2002). Considering these limitations of stimulant treatment, the need for examining the utility of psychosocial treatments remains.

Psychosocial treatments for ADHD can be divided into four categories (Pelham and Murphy, 1986, Pelham et al., 1998), (1) clinical behavior therapy (e.g., behavioral parent training) (2) direct contingency management (e.g., behavioral classroom interventions), (3) intensive packaged behavioral treatments (e.g., a combination of clinical behavior therapy and direct contingency management), and (4) cognitive-behavioral treatments (e.g., verbal self-instructions, social skills training, problem-solving strategies, and cognitive modeling).

Several authors, using the task force criteria (Task Force on Promotion and Dissemination of Psychological Procedures, 1995), conclude that (1) clinical behavior therapy, (2) direct contingency management (behavioral treatments, such as behavioral parent training, behavioral classroom interventions) and (3) intensive multimodal behavioral treatments, meet criteria for empirically supported treatments for ADHD, but that (4) cognitive-behavioral treatments do not (Chambles & Ollendick, 2001; Hinshaw et al., 2002; Pelham et al., 1998). There is only limited evidence for certain types of cognitive-behavioral interventions, such as social skills training and problem-solving interventions, which may only show efficacy in the treatment of ADHD, when combined with intensive multimodal behavioral treatment packages (Pelham et al., 1998). Results of a meta-analysis of school-based interventions for ADHD showed that behavioral interventions were more effective than cognitive-behavioral interventions in terms of improving classroom behavior (DuPaul & Eckert, 1997). On academic performance, however, cognitive-behavioral school-based interventions were more effective than behavioral school-based interventions (DuPaul & Eckert, 1997). Up to now, however, no systematic comparison of effect-sizes between the cognitive-behavioral and behavioral treatments is present, other than for school-based interventions for children with ADHD.

A disadvantage of psychosocial treatments is that considerable room for improvement remains, especially in the domain of peer relationships (Pelham et al., 1998). It has been suggested that more intensive psychosocial treatments may be necessary (Wells et al., 2000, Pelham et al., 1998). The limitations of stimulant and psychosocial treatments have led to combining these two treatment modalities (Pelham et al., 2000), since combined treatment is suggested to enhance the treatment effects of just one treatment modality (Pelham et al., 1998, Pelham and Waschbusch, 1999).

This enhancement of treatment effects by means of combining the methylphenidate and psychosocial treatments may work through different mechanisms (Pelham & Murphy, 1986). First, the two treatments may potentiate each other, yielding a combined effect that is greater than the total of the two treatment effects. Second, the two treatments may interact to inhibit each other, yielding an effect that is less than the effects of either treatment. Third, the effect may be additive, equaling the total of both treatment effects. Finally, reciprocation may occur in which the combined treatment has the same effect as one of both treatments (Pelham & Murphy, 1986). Comparing the effect-sizes of the two separate treatments and their combination can clarify the mechanism underlying these enhanced effects.

Psychosocial treatments may improve outcome on some symptoms, and medication may improve outcomes on other symptoms, while both interventions may be necessary to maximize change in or normalize functioning on all areas of functioning (Pelham & Murphy, 1986). Combined treatments are often suggested to enhance the effects of methylphenidate especially on ADHD-related symptoms, such as social behavior, oppositional symptoms and academic functioning (e.g., Klein et al., 2004, Wells et al., 2000). Also, combined treatment is expected to produce long-term benefits in a variety of functional domains (Klein et al., 2004). Laboratory studies have shown that low doses of methylphenidate and behavioral treatments have additive effects (e.g., Carlson et al., 1992, Pelham et al., 1993), but behavioral treatments did not have additional effects to high doses of methylphenidate. It should be noted, however, that combined treatments have been understudied compared to pharmacological or psychosocial interventions alone (Pelham et al., 2000).

Several reviews (e.g., Farmer et al., 2002, Greenhill et al., 1999, Hinshaw et al., 1998, Pelham et al., 1998, Pelham and Fabiano, in press) and meta-analyses (Klassen et al., 1999, Schachter et al., 2001, Spencer et al., 1996, Swanson, 1993) have been published on treatments of childhood ADHD, but to date no meta-analysis has been conducted that systematically compares the effect-sizes of psychosocial, stimulant treatments and their combination, on ADHD symptoms and related symptom domains.

In a critical appraisal of prior reviews and meta-analyses on treatment of ADHD of Jadad et al. (1999) it is shown that most reviews on ADHD had major methodological flaws, since the methods used by the authors to identify, select and assess information were not described properly. More importantly, only one of the selected thirteen reviews on treatment of ADHD has dealt with the efficacy of psychosocial treatments, focusing on school-based treatments (DuPaul & Eckert, 1997).

The current meta-analysis was designed to assess the relative efficacy of methylphenidate, psychosocial treatments, and their combination on four outcome domains; ADHD, ODD symptoms, social skills and academic functioning. To date, all studies on combined treatments have included short-acting methylphenidate conditions only. Therefore, in the present review only methylphenidate studies using short-acting methylphenidate were included. Since the main interest of the present study was to examine the clinical utility of these treatments and because the great majority of children with ADHD is being treated in clinical settings, only studies conducted in clinical settings were included, rather than studies in analogue or controlled settings.

Several authors have argued that, given the multifaceted nature of ADHD and its impairments and the fact that considerable room for improvement remains after psychosocial treatment, regular, short-term psychosocial treatments may not be adequate for many ADHD children. More intensive, lengthy psychosocial treatments programs may be necessary for these children (e.g. Pelham & Waschbusch, 1999). Consequently, duration of treatment may affect the efficacy of treatment (Barkley, 2002, Pelham et al., 1998, Schachter et al., 2001, Wells et al., 2000). In this study we investigated the relation between duration of treatment and efficacy of treatment.

Although it has been often suggested that cognitive-behavioral treatments do not meet criteria for empirically supported treatments, and do not provide clinically significant changes in the behavior of children with ADHD (Pelham et al., 1998, Chambles and Ollendick, 2001), a systematic comparison of effect-sizes of behavioral and cognitive-behavioral interventions for children with ADHD is not yet available. Therefore, in the present study the effect-sizes of “cognitive-behavioral” and “behavioral” treatments were compared.

In psychosocial treatment research single-case designs and within-subjects designs are used more often than between subjects designs (Pelham & Fabiano, in press). The review of Pelham and Fabiano (in press) on evidence-based psychosocial treatments of the last 10 years, reports very large effect-sizes for single-case studies on behavioral interventions. Actually, the single-case studies have considerably larger effect-sizes than the between-group studies on behavioral interventions (Pelham & Fabiano, in press). However, given the potential selection bias involved in such single-case designs (Kazdin, 2003), our meta-analysis is limited to between-group designs.

Section snippets

Methods

Studies were retrieved that were published between January 1, 1985 and September 30th, 2006. We searched for studies in the English language in the following databases: PubMed, PsycInfo and ISI Web of Science. Also e-publishments ahead on the internet were included in this search. The reference lists of published articles were then used to locate other relevant studies. The following keywords were used for all searches: ADHD, child and treatment. A total of 397 articles were found. Studies

Statistical analyses

Analyses were conducted using a computer program developed by Borenstein and Rothstein (1999). The within group effect-sizes were calculated for each study using Cohen's d statistic (Cohen, 1988) and was defined as the difference between the pre- and post-intervention mean divided by the pooled SD. In this study a positive effect-size was taken to indicate improvement. The mean weighted effect-size, was weighted by sample size of the individual studies. To calculate the mean weighted

Description of the studies

Twenty-six studies met the inclusion criteria. These studies are described in Table 1. For some studies data were missing. In that case, authors were contacted, However, some authors were not able to provide missing data. In that case studies were excluded from analyses. In several instances, especially for the combined condition, only a few studies were available.

Meta-analytic procedures may be applied to as few as two studies, but with very few studies meta-analytic results can be very

Discussion

The present meta-analysis investigated the efficacy of short-acting methylphenidate, psychosocial treatments and their combination on ADHD and ODD/CD symptoms, social behavior and academic functioning in school-aged children with ADHD. Several databases were searched for studies published between 1985 and 2006 that employed a randomized controlled design, were conducted in outpatient settings and focused on 6 to12 year old children. Twenty-six studies were retrieved that met these inclusion

Strengths and limitations

The studies examined in our meta-analysis often suffered from low statistical power, due to a small number of participants and multiple outcome measures. Meta-analysis enhances power by combining the results of all underpowered studies, and therefore yields statistically better informed conclusions than a narrative review. This may explain the difference in the results from this meta-analysis and the results of previous narrative reviews, in which an additional effect of psychosocial

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