To investigate the incidence, persistence, and consequences of insomnia and their associations with psychological health and pain.A population based, longitudinal, cohort study using postal questionnaires at baseline and 12-month follow-up. Sleep problems in the past month were assessed using 4 questions: insomnia was defined as having at least 1 of the sleep problems "on most nights." Questions about psychological health, presence of pain at different sites, and demographic details were included in the questionnaire.Five general practices in Staffordshire, UK.The questionnaire was mailed to a random sample of 4885 adults aged 18 years and over registered with these practices. There were 2662 questionnaires returned.Of the responders, 2363 completed all 4 sleep questions at baseline: 870 (37%) had insomnia and 1493 (63%) did not have insomnia. Of those without insomnia at baseline, the incidence of insomnia at 12 months was 15%, and this was significantly associated with baseline anxiety, depression, and pain. Of those who did have insomnia at baseline, 69% had insomnia at 12-month follow-up; persistence of insomnia was significantly associated with older age. Insomnia at baseline was significantly associated with incidence of anxiety, depression, and widespread pain at 12-month follow-up.Insomnia is common and often persistent. Older people appear more vulnerable to persistent symptoms. Our results provide evidence that the common problems of insomnia, pain, and psychological distress are intertwined and suggest that combined approaches to treatment may be needed to reduce the onset and persistence of these problems in the community.