Figure 2.

Longitudinal relationships between insomnia and depression. Cross-sectional and longitudinal relationships between “pure” insomnia (including insomnia symptoms and occasional, recurrent brief, 2- to 3-week insomnia, and 1-month insomnia) “pure” depression (including major depressive episonde, minor depression, dysthymia, and depressive symptoms) and insomnia comorbid with depression (insomnia + depression) were analyzed using log-linear models. The strength of the associations is represented by the different line styles, as indicated in the figure. Numbers represent odds ratios. *Indicates that the odds ratio between depression in 1988 and 1993 was 0 and thus not interpretable. Panel a: longitudinal associations within pure insomnia, insomnia with comorbid depression, and pure depression conditions. Panel b: Longitudinal associations between pure insomnia and the other 2 conditions, as well as longitudinal associations between pure depression and the other 2 conditions. Panel c: Longitudinal associations between insomnia comorbid with depression and the other 2 conditions.