To Örebro University

Background: The aim of this investigation was to examine the longitudinal association between change ininsomnia status and the development of anxiety and depression in the general population.

Methods: A survey was mailed to 5000 randomly selected individuals (aged 18–70 years) in two Swedish counties.After 6 months, a follow-up survey was sent to those (n = 2333) who answered the first questionnaire. The follow-up survey was completed by 1887 individuals (80.9%). The survey consisted of questions indexing insomniasymptomatology, socio-demographic parameters, and the Hospital Anxiety and Depression Scale. Change ininsomnia status was assessed by determining insomnia at the two time-points and then calculating a change indexreflecting incidence (from non-insomnia to insomnia), remission (from insomnia to non-insomnia), or status quo (nochange). Multivariate binary logistic regression analyses were used to examine the aim.

Results: Incident insomnia was significantly associated with an increased risk for the development of new cases ofboth anxiety (OR = 0.32, p < .05) and depression (OR = 0.43, p < .05) 6 months later. Incident insomnia emerged alsoas significantly associated with an elevated risk for the persistence of depression (OR = 0.30, p < .05), but not foranxiety.

Conclusions: This study extends previous research in that incidence in insomnia was shown to independentlyincrease the risk for the development of anxiety and depression as well as for the maintenance of depression. Thefindings imply that insomnia may be viewed as a dynamic risk factor for anxiety and depression, which might haveimplications for preventative work.