This was my first APSARD conference and I was not sure what to expect. I knew APSARD as a psychiatry conference and assumed many presentations would focus on medication management of ADHD symptoms. Although some symposia addressed medication issues, symposia topics covered the waterfront, from etiological models involving genetics and neuroscience to clinically-oriented sessions about assessment and treatment to big data epidemiological approaches. A resounding theme across many symposia was our struggle to understand how and why ADHD symptoms develop. The causal role of environmental factors in the pathogenesis of ADHD were considered in several symposia. During the Sunday morning plenary session, Drs. Edmund Sonuga-Barke and Anita Thapar addressed the shifting conceptualization of ADHD from a biologically-based disorder to a transactional disorder involving a complex interplay between genetic predisposition and environmental processes. Dr. Sonuga-Barke discussed results from the English and Romanian Adoptee Study, which demonstrated that severe environmental deprivation early in life can cause ADHD symptoms. Dr. Thapar outlined the complexities in parsing genetic from environmental risk given that shared genetic liability for ADHD may be driving maladaptive features of parenting as well as child symptoms. She discussed how longitudinal adoption design studies can isolate genetic from environmental risk and add specificity to how environmental processes contribute to ADHD symptoms (and how ADHD symptoms contribute to environmental processes). These talks, along with many others, highlighted how our conceptualization of ADHD is in flux. There are many unanswered etiological questions and future research is needed to better understand how environmental processes intersect with biological vulnerability. Although I left the conference feeling less certain about what I thought I knew, I also left feeling energized to keep up the search for the how and why of ADHD.