A study published in the April 1 issue of the journal SLEEP confirms the persistent nature of insomnia and the increased risk of subsequent depression among individuals with insomnia.
The study, conducted by Jules Angst, MD, of Zurich University Psychiatric Hospital in Switzerland, focused on 591 young adults, whose psychiatric, physical, and sleep symptoms were assessed with six interviews spanning 20 years. Four duration-based subtypes of insomnia were distinguished: one-month insomnia associated with significant distress, two-to-three-week insomnia, recurrent brief insomnia, and occasional brief insomnia.
According to the results, the annual prevalence of one-month insomnia increased gradually over time, with a cumulative prevalence rate of 20 percent and a greater than two-fold risk among women. In 40 percent of subjects, insomnia developed into more chronic forms over time. Insomnia either with or without comorbid depression was highly stable over time. Insomnia lasting two weeks or longer predicted major depressive episodes and major depressive disorder at subsequent interviews. Seventeen to 50 percent of subjects with insomnia lasting two weeks or longer developed a major depressive episode in a later interview. “Pure” insomnia and “pure” depression were not longitudinally related to each other, whereas insomnia comorbid with depression was longitudinally related to both.