Background: Little is known about the relationship between attention-deficit/hyperactivity disorder (ADHD) subtypes and substance-use disorder (SUD). As there is literature suggesting different subtype phenotypes, there may be subtype differences in regard to the risk for developing SUD and substance treatment response.
Objectives: To characterize the sample in a Clinical Trials Network (CTN) study according to ADHD subtypes and baseline psychosocial and substance-use characteristics and to compare subtypes on response to treatment.
Methods: Secondary analyses on data collected from adolescents (n = 276) diagnosed with ADHD and SUD (non-nicotine) and treated with stimulant medication or placebo and cognitive behavioral therapy (CBT) for substance use. Participants were characterized as inattentive or combined ADHD subtype and compared on baseline characteristics and treatment outcome.
Results: The combined subtype presented with more severe SUDs and higher rates of conduct disorder. There were a greater proportion of boys with inattentive subtype. The inattentive subtype appeared less ready for treatment (greater University of Rhode Island Change Assessment precontemplation scores) with poorer coping skills (poorer problem-solving and abstinence focused coping) at baseline. However, the two subtypes responded equally to treatment even after controlling for baseline differences.
Conclusions: Findings from this large community sample indicate that there were no subtype differences in treatment response, although there were differences in terms of substance use, antisocial behavior, readiness for treatment, and gender prior to treatment.
Scientific significance: This study is the first to report on subtype differences for treatment response for non-nicotine SUD in a comorbid ADHD-SUD population. Despite some baseline differences, both subtypes responded equally to treatment, suggesting limited relevance for subtype designation on treatment planning.