Introduction: Attention Deficit/Hyperactivity Disorder (ADHD) is one of the most prevalent psychiatric disorders of childhood, which persists into adulthood in 10-60% of the cases. A growing body of data suggests that pharmacotherapy of the disorder is efficacious but a comprehensive summary of available evidence from clinical trials is lacking. The aim of the article was to provide a systematic review of therapeutic efficacy observed in the pharmacological treatment of ADHD based on data from controlled clinical trials.
Methods: We used the search engines PubMed and Medline to identify relevant clinical trials. Studies with short term, double-blind and parallel design were selected for the review.
Results: Altogether, 11 trials were included in the review. Our systematic review indicated that adult ADHD is treated with the same medications as the childhood form of the disorder, including psychostimulants as the first line of treatment, antidepressants as the second line, and more recently atomoxetine as well. In view of the fact that only relatively few investigations were available within the individual drug classes, no statistically significant differences could be demonstrated among the classes; thus, our data with regard to effect size should only be considered as descriptive. Most of the investigations focused on psychostimulants, which produced a strong effect size vs. placebo. With regard to atomoxetine, only a few studies were found, in which, however, a large number of subjects were enrolled, representing the largest studies in the literature. The effect size of atomoxetine in these studies was in the medium range. This result is noteworthy since the average age of the subjects in these studies was the highest among the selected studies (more than 40 years, in contrast to less than 40 years in all other studies); this (considering the chronicity of the illness) is viewed as a predictor of poor therapeutic response. Among antidepressants, most clinical trials tested bupropion; based on these trials, this compound is expected to produce an effect size in the medium range.
Conclusions: Pharmacologic agents affecting the dopamine and norepinephrine system have been found to be effective in reducing the symptoms of adult ADHD. In half of the trials, the tested drug was a psychostimulant. The effect sizes of the studies with amphetamine, methylphenidate and dexmethylphenidate were in the high effect size range, and owing to the small number of investigations, we could not discriminate between these drugs. Based on the data available from the literature, non-stimulant medications are indicated when substance dependence or abuse is in the history, or when the side effects of psychostimulants are not tolerated by the patient.