Effect of Past Pharmacotherapy for Attention-Deficit/Hyperactivity Disorder on Substance Use Disorder

Background: Substance use disorders (SUDs) are a considerable public health problem. Attention-deficit/hyperactivity disorder (ADHD) frequently occurs in patients with SUD. Several studies demonstrated that ADHD constitutes a significant risk factor for the development of SUDs and suggest that childhood ADHD pharmacotherapy might help prevent development of SUD. Objectives: The study aimed to explore the effect of childhood ADHD pharmacotherapy on later life's functional impairment and substance use patterns. Methods: Treatment-seeking SUD patients with ADHD (n = 52) were recruited from various rehabilitation facilities in South Africa. Adult ADHD individuals without SUD (n = 48) were recruited from clinicians, retail pharmacies, and the general public. SUD participants in rehabilitation facilities were screened for and diagnosed with ADHD. Lifetime substance use was assessed using self-report. ADHD-related functional impairment was assessed by the Weiss Functional Impairment Rating Scale (WFIRS). Information on present and lifetime use of ADHD medication was obtained. Clinical outcomes between those with and without a history of ADHD pharmacotherapy were compared. Results: Medicated participants (n = 59) showed lower levels of ADHD-related impairment across all functional domains (p < 0.001), compared to non-medicated participants (n = 41). They also consumed less alcohol (p = 0.04), cannabis (p < 0.001), and illicit drugs (p = 0.006) compared to the non-medicated group. Furthermore, medicated participants had a lower frequency of tobacco use compared to non-medicated participants (p = 0.04). ADHD patients without SUD also more often received medication (100% vs. 18.6%; p < 0.001) and for a longer time (121.10 vs. 9.52 months; p < 0.001). Conclusion: Childhood ADHD pharmacotherapy might be associated with a decreased risk for substance use in adulthood and lower ADHD-related impairment. Despite study limitations, these findings underline the importance of early ADHD detection and treatment, which might prevent SUD.