This epidemiological study from Australia, spanning 16 years, explores the influence of early language delays over time on outcomes in affected adults. Based on vocabulary skills at age five, the study population was classified into four groups: persistently good, persistently poor, improved and deteriorated. The individuals were then re-evaluated at age 21 and the association between their vocabulary and mental health, educational and vocational outcomes were recorded. The study results indicated that adults with persistently poor vocabulary or deteriorated vocabulary were unlikely to have completed secondary school and were less likely to be employed. In addition, these individuals were at a higher risk of suffering from affective disorders, substance abuse or misuse. The study provided evidence that irrespective of time of onset of language delays, impaired vocabulary in adults was associated with poor outcomes. The authors suggest that clinicians and educators should anticipate these adverse long- term outcomes and attempt to support children or adolescents with language delays to prevent them.