Attention-deficit hyperactivity disorder (ADHD) and substance use disorders (SUDs) may have common etiologies. ADHD is more prevalent in patients with substance use disorders, and this pattern is consistent across different substances of abuse. Individuals with SUDs and ADHD exhibit significant variations in their clinical presentations. The developmental trajectory of ADHD to SUDs is complex: ADHD symptoms appear first in some patients but not in others. Many patients present with a heterogeneous collection of psychiatric and substance use co-morbidities, and these symptoms change over time. ADHD symptom severity is also highly variable, and more severe ADHD symptoms worsen co-morbid SUDs and complicate treatment. New longitudinal studies with innovative methods in high-risk populations and in community-based samples may clarify issues related to patient-treatment matching. When closely monitored, psychostimulant and other adjunct medications can be safely used to treat ADHD in this population, and such treatment may also improve outcome of SUDs. In particular, emerging evidence suggests individual-level tailoring ("precision medicine") approaches may represent a key pathway to improve clinical outcome.
Keywords: Addiction; Attention-deficit hyperactivity disorder; Clinical trials; Cocaine; Comorbidity; Dopamine; Longitudinal study; Precision medicine; Stimulants; Substance use disorders.