Effects of intervention design on engagement and outcomes in digital self-help for insomnia - factorial RCT. - Amira Hentati; Nils Hentati Isacsson; H. A. Rosen; Susanna Jernelöv; Viktor Kaldo; Brjánn Ljótsson; Erik Forsell; Nils Lindefors; Martin Kraepelien (npj Digit. Medicine, 2025)