The aim of this study was to examine whether ADHD is a dimensional trait in the adult general population. We studied whether an increased number of ADHD symptoms was associated with higher comorbidity, exposure to risk factors (childhood abuse and parental psychopathology), and disability. We ascertained whether even low numbers of ADHD symptoms were associated with an increased burden of disease. Data were used from the second wave of the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2, N = 5303). NEMESIS-2 is a nationally representative face-to-face survey on mental health of the Dutch general population. ADHD symptoms, mental comorbidity, and disability were assessed using the Adult ADHD Self-Report Scale Screener, the Composite International Diagnostic Interview version 3.0, and the Medical Outcomes Study Short Form Health Survey, respectively. Dose-response relationships were found between the number of ADHD symptoms and Axis I and II mental disorders; exposure to risk factors; and mental and physical disability. Our study supports the notion that ADHD is a dimensional trait in the adult general population. Even low numbers of symptoms were associated with an increased burden of disease, and therefore these should be identified and treated.