ABSTRACT
BACKGROUND: ADHD is an important risk factor for the development of substance use disorders (SUD). AIM: To provide an overview of recent Dutch research into the prevalence of ADHD in SUD populations and the neurobiological substrate of the reduced effect of pharmacological treatment of this patient group. METHOD: We describe three studies: a meta-analysis and meta-regression analysis of the prevalence of ADHD in 6689 SUD patients; a cross-sectional study of the prevalence of ADHD and several other psychiatric disorders in 193 methadon maintenance patients, and finally a study in which the availability and occupation of dopamine transporters before and after methylphenidate treatment were measured using SPECT scans in 24 ADHD patients with and without cocaine addiction. RESULTS: The prevalence of ADHD in SUD patients is estimated to be 23.1% (95% confidence interval 19.4-27.2). This prevalence is influenced by the diagnostic instrument for ADHD and by the substance of abuse: cocaine is associated with a lower ADHD prevalence than other substances. The prevalence found among methadone maintenance patients was similar, namely 24.9%; additional comorbid psychiatric disorders were also frequently present. In the imaging study, lower availability of dopamine transporters and lower occupation by methylphenidate were found in cocaine-dependent ADHD patients than in ADHD patients without SUD. CONCLUSION: These studies confirm the high prevalence of ADHD in SUD patients, and provide a possible explanation for the reduced efficacy of methylphenidate in this patient population.
