© 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).Attention-deficit/hyperactivity disorder (ADHD) exerts lifelong impairment, including difficulty sustaining employment, poor credit, and suicide risk. To date, however, studies have assessed selected samples, often via self-report. Using mental health data from the entire Swedish population (N = 11.55 million) and a random sample of credit data (N = 189,267), we provide the first study of objective financial outcomes among adults with ADHD, including associations with suicide. Controlling for psychiatric comorbidities, substance use, education, and income, those with ADHD start adulthood with normal credit demand and default rates. However, in middle age, their default rates grow exponentially, yielding poor credit scores and diminished credit access despite high demand. Sympathomimetic prescriptions are unassociated with improved financial behaviors. Last, financial distress is associated with fourfold higher risk of suicide among those with ADHD. For men but not women with ADHD who suicide, outstanding debt increases in the 3 years prior. No such pattern exists for others who suicide.