Studies have assessed the association between a longer duration of untreated symptoms and outcome for psychoses in specialist care. We investigated the effect of longer duration on the outcome of common psychiatric disorders in primary care, where most patients are treated. Patients presenting to primary care for new episodes in 10 countries were recruited into a prospective cohort study. Information on duration of untreated symptoms and psychosocial status was collected for 351 individuals using standardised instruments and this was repeated 1 year later. At 1-year follow-up, longer duration was associated with worse psychiatric outcome even after controlling for potential confounders.