Objectives <p>Attention-deficit/hyperactivity disorder (ADHD) is associated with a range of mental and physical health comorbidities, including depression and gastrointestinal problems. ADHD is further associated with higher rates of adverse childhood experiences (ACEs). The double-jeopardy model assumes that ADHD and ACEs are cumulative risk factors affecting health outcomes. We aimed to test this core prediction of the model.</p> Methods <p>Participants were recruited via the online platform Prolific. A sample of <i>n</i> = 131 adults with ADHD and a propensity-matched (age, sex) comparison group of adults without ADHD took part in the study (<i>N</i> = 262). Data was analysed using robust statistical methods, including Yuen’s t-test (group differences), Spearman rank correlations, and logistic binomial regression models.</p> Results <p>The ADHD group reported higher rates of ACEs, mental health, and gastrointestinal problems (medium to large effects). ADHD and ACEs both predicted emotional problems, but only ADHD predicted GI symptoms. To further explore this effect, we conducted a series of sensitivity analyses. Emotional problems predicted the presence of GI symptoms in addition to ADHD. Experiences of deprivation, but not threat, predicted GI symptoms over and above the effect of ADHD.</p> Conclusion <p>The findings from this study support the double-jeopardy model by showing that ADHD and ACEs may be cumulative risk factors for the development of comorbid emotional problems.</p>