Primary Outcomes

Both insomnia and depression severity are considered primary outcomes since the study focuses on these two comorbid diagnoses.

Insomnia Severity. Insomnia severity is measured with the ISI, a scale with 7 items and a score ranging from 0–28 points; higher score equals more severe insomnia. It has an internal consistency of Cronbach’s α = 0.76, has high concurrent validity with sleep diary and polysomnography, and is sensitive to change after both psychological and pharmacological treatment [27].

Depression Severity. Depression severity is measured with the MADRS-S, a 9-item scale with a score ranging from 0–54 points; higher score equals more severe depression. MADRS-S has an internal consistency of Cronbach’s α = 84 [46], is stable over time in non-improving patients, and is sensitive to change after treatment [28]. ISI and MADRS-S were distributed online.