• Sleep efficiency, total sleep time, total wake time, sleep-onset latency, wake after sleep onset, and early morning awakening [ Time Frame: Measured at baseline and Months 3 and 9 ] [ Designated as safety issue: No ]
  
• Insomnia Severity Index [ Time Frame: Measured at baseline and Months 3 and 9 ] [ Designated as safety issue: No ]
  
• Beliefs and attitudes about sleep as measured by the Dysfunctional Beliefs and Attitudes about Sleep scale (DBAS 16) [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Sleep knowledge [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Fatigue as measured by the Multidimensional Fatigue Symptom Inventory (MFSI) [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Depression as measured by the Beck Depression Inventory 2 [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Anxiety as measured by the State-Trait Personality Inventory (STPI) [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Cognitive functioning as measured by the Headminder's Customized Research Tool (CRT) and Conner's Continuous Performance Test (CPT) [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  

• Cost-benefit measures (direct and indirect costs associated with insomnia) [ Time Frame: Measured at baseline and Months 3 and 9 ] [ Designated as safety issue: No ]
  
• Quality of life as measured by the SF-12 Health Survey [ Time Frame: Measured at baseline and Month 3 ] [ Designated as safety issue: No ]
  
• Feedback regarding use of the internet intervention, including post-treatment ratings of treatment credibility, acceptability, effectiveness, satisfaction, and ease of use of the internet [ Time Frame: Measured at Month 3 ] [ Designated as safety issue: No ]
  

Insomnia is a disorder that is characterized by a perception or complaint of inadequate or poor-quality sleep. Symptoms of insomnia include difficulty falling asleep, waking frequently during the night and having difficulty returning to sleep, waking too early in the morning, and unrefreshing sleep. Insomnia may also cause problems during the day, such as tiredness, difficulty concentrating, and irritability. Cognitive behavior therapy (CBT) has been found to have significant short- and long-term benefits for people with insomnia. Access to CBT for many people, however, is limited, due to the high cost of treatment and a lack of trained professionals in some locations. Delivering CBT via the internet could help make the treatment more widely available. This study will evaluate the effectiveness of an online CBT intervention in improving sleep, mood, and cognitive functioning in people with insomnia.

Participants in this open label study will be randomly assigned to receive the online CBT intervention either immediately or after a 4-month waiting period. Participants will use the online program for 1 to 2 hours per week for 8 weeks. Participants will keep track of their sleep patterns for the first and last 2 weeks of a 4-month period by keeping a daily diary and wearing a wrist watch device that monitors movement. All participants will report to the study site for baseline evaluations before beginning treatment and for final evaluations upon completing the program, about 4 months after study entry.