Purpose Disparities in psychological distress across socioeconomic status and sex persist throughout adulthood as cohorts age. In this study, we investigate the extent to which this persistence represents either (i) a single set of individuals who at the start of adulthood show distress that is chronic and long lasting or (ii) different sets of individuals that have a staggered onset of short-term distress throughout adulthood. Methods We use path analysis on data from the National Child Development Study, a longitudinal cohort study that assessed psychological distress at ages 23, 33, and 42 years. Results About 80% of distress disparities at age 42 result from chronic distress that was present in a single set of individuals at least 19 years earlier at the beginning of adulthood. Conclusions These results support a targeted approach to the reduction of distress disparities that focuses on young adults with high levels of distress and seeks to improve their long-term mental health.