AbstractBackgroundCo‐occurring (overlapping) irritable bowel syndrome (IBS), functional dyspepsia (FD), and heartburn has been observed. However, whether it is a distinct entity has not been established, nor what clinical, demographic, lifestyle, and psychological traits are associated with it. This study sought to estimate the prevalence and temporal stability of this overlap and to identify features specific to it in order to gain some insights into the potential etiopathogenesis.MethodsTwo waves of a survey to a population‐representative sample were conducted 3 years apart, recruiting 1312 individuals for this study. The chance‐expected probability of complete overlap (CO) was calculated and compared with the observed CO. A range of demographic, lifestyle factors, medical diagnoses, sleep quality, and psychological distress were tested to identify predictors of overlap using logistic regression.Key ResultsCO was observed in 2.1% (95% confidence interval 1.9, 3.7) of the sample and was closely replicated in wave 2 at 2.0%. The observed CO was greater than expected by chance (0.2%) to a statistically significant extent (p < 0.001). Overlap between IBS subtypes, FD subtypes, and heartburn was also elevated above chance expectation. Individuals with CO were separately differentiated from others with respect to elevated rates of self‐reported medically diagnosed asthma, elevated psychological distress score, and elevated impact on sleep quality. The discrimination provided by these factors was further independent of age and sex.Conclusions and InferencesOverlap between IBS, FD, and heartburn (GERD) appears to be a distinct entity that has a profile including psychological morbidity, sleep disturbance, and elevated rates of atopy.