To Örebro University

Objective: The objective was to investigate the role of psychiatric and somatic conditions in incident and persistent insomnia.

Design: This was a prospective study with 3 measurement points over 1.5 years.

Setting: The participants were sent a survey to their home addresses.

Participants: A survey was sent out to 5000 random individuals (18-70 years) in 2 Swedish counties. To those who returned the baseline questionnaire (n = 2333), 2 follow-up surveys (6 and 18 months later) were sent out and completed by 1887 and 1795 individuals, respectively.

Measurements: The survey contained questions about sociodemographic factors and insomnia symptomatology, the Hospital Anxiety and Depression Scale, and items assessing 12 forms of somatic conditions (eg, heart disease and headache).

Results: Baseline depression, headache, and number of psychiatric and somatic conditions were found to be independent risk factors for incident insomnia. Also, deterioration in depression and heart disease status and increased number of conditions over time increased the risk for insomnia incidence. Anxiety; depression; pain in neck, back, or shoulders; and headache at baseline were found to significantly discriminate between those with persistent insomnia and those with persistent normal sleep. Those with persistent insomnia also reported a higher number of conditions relative to those with persistent normal sleep. None of the psychiatric or somatic conditions were found to be associated with persistence of insomnia relative to remission of insomnia.

Conclusion: The current study suggests that both psychiatric and somatic conditions are involved in the incidence but not in the persistence of insomnia. Clinical and theoretical implications of the results are discussed.