Experimental: Digital cognitive behavioral therapy (dCBT-I)

CBT-I is designed to change sleep habits and scheduling factors that affect sleep, and to address misconceptions about sleep and insomnia that perpetuate sleep difficulties. The investigators will employ SHUTi, which is an extensively studied dCBT-I program. SHUTi is intended to improve insomnia symptoms by providing neurobehavioral intervention (cognitive behavioral therapy for insomnia - CBT-I) in adults with chronic insomnia. It is a six-core internet-delivered CBT-I web-based app that is run through a browser. It is accessible via iPhone/iPad, Android phone/tablet, computer or laptop (any device with a browser). SHUTi follows evidence-based CBT-I principles.

Active_comparator: Patient Education (PE)

Participants will be given access to a patient education website. It will provide nontailored material about insomnia symptoms; the impact, prevalence, and causes of insomnia; and basic lifestyle, environmental, and behavioral strategies to improve sleep.