Introduction: Just Say No? New Insights About Change Versus Constancy in Substance Use Behavioral Decisions in Youth With and Without ADHD.

Despite enormous social-psychological and economic consequences of substance abuse in youth and young adults, too little is known about effective interventions among substance users, both with and without ADHD. This special issue reports on four linked investigations that employed a novel research strategy when the Multimodal Treatment Children with ADHD Study (MTA) participants were between ages 21.7 and 27.3 years old (14-16 years after initial assessments). Using combination of in-depth qualitative narrative interviews and quantitative analyses ("mixed methods") of 183 participants from four to six original MTA sites, investigators sought to obtain a more complete understanding of factors contributing to youths' substance use (SU) initiation, maintenance, and desistence, (both among youth with ADHD and control participants). The articles in this special issue illuminate important new insights about possible influences contributing to SU, particularly persistent use/abuse. Findings also illustrate the benefits of mixed-methods studies, not only to better understand the linkages between ADHD and SU, but also to understand other areas of child/adult psychopathology.